CBSE Class 10 Science HOTs Periodic Classification of Elements

MCQ Questions for NCERT Class 10 Science Periodic Classification of Elements

Question. Pick out the chemically most reactive elements from the given triads.
Li, Na, K F, Cl, Br
(a) Li and F
(b) Li and Br
(c) K and F
(d) K and Br

Answer : C

Question. Identify the wrong sequence of the elements in a group
(a) Ca, Sr, Ba
(b) Cu, Au, Ag
(c) N, P, As
(d) Cl, Br, I

Answer : B

Question. An element ‘X’ is placed in group 13 and third period of the Periodic Table. It burns in oxygen to form an oxide which is amphoteric in nature. Identify the chemical formula of its chloride
(a) CCl₄
(b) BCl₂
(c) GaC_l3
(d) AlCl₃

Answer : D

Question. Arrange the following elements into the increasing order of their metallic character along a period.
(a) S < Si < P < Al
(b) S < P < Si < Al
(c) Si < P < S < Al
(d) Si < S < P < Al

Answer : B

Question. In the Modern Periodic Table calcium (Z = 20) is surrounded by the elements with atomic numbers 12, 19, 21, and 38 which of the following will have physical and chemical properties resembling calcium.
(a) 12, 20, 38
(b) 12, 19, 20, 38
(c) 19, 20, 38
(d) 12, 19, 20

Answer : A

Question. Which is not true about noble gases?
(a) They are non-metallic in nature
(b) They exist in atomic form
(c) They are radioactive in nature
(d) Xenon is the most reactive among these

Answer : C

Question. The elements A, B and C belong to groups 1, 14 and 17 respectively of the Periodic Table. Which two elements will form ionic compounds?
(a) A and B
(b) A and C
(c) B and C
(d) None

Answer : B

Question. Which of the following is a transition element ?
(a) Pb
(b) As
(c) A1
(d) Ni

Answer : D

Question. In Mendeleev’s Periodic Table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the periodic table later ?
(a) Germanium
(b) Chlorine
(c) Oxygen
(d) Silicon

Answer : A

Question. An element has atomic number 17. To which group, period does it belong ? It is metal or non-metal ?
(a) 7^th group, 2^nd period, Non-metal
(b) 17^th group, 3^rd period, Non-metal
(c) 7th group, 3^rd period, Metal
(d) 17^th group, 3^rd period, Metal

Answer : B

Question. Newlands relation is called
(a) Musical Law
(b) Law of Octaves
(c) Periodic Law
(d) Atomic Mass Law

Answer : B

Question. Which of the following set of elements is written in order of their increasing metallic character ? 
(a) Be<Mg<Ca
(a) Na<Li<K
(a) Mg<Al<Si
(a) C<O<N

Answer : A

Question. Which one of the following statements is not correct about the trends in the properties of the elements of a period on going from left to right?
(a) The oxides become more acidic
(b) The elements become less metallic
(c) There is an increase in the number of valence electrons
(d) The atoms lose their electrons more easily

Answer : D

Question. In Mendeleev’s Periodic Table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the Periodic Table later?
(a) Chlorine
(b) Silicon
(c) Oxygen
(d) Germanium

Answer : D

Question. The element which has least tendency to lose electron is
(a) H
(b) Li
(c) He
(d) Ne

Answer : C

Question. Which of the following is non-metal and to which group does it belong?
(a) Lead
(b) Gallium
(c) Bromine
(d) Cadmium

Answer : C

Question. Which one of the following statements is not correct about the trends in the properties of the elements of a group on going down in a group?
(a) The chemical reactivity of metals increases.
(b) The metallic character of elements increases.
(c) The size of the atom increases.
(d) The valence electrons increase.

Answer : D

Question. Which of the following oxide is most basic?
(a) Li₂O
(b) Na₂O
(c) K2O
(d) Cs₂O

Answer : D

Question. The metal which is hard and has high melting point and used in filaments of electrical bulbs is
(a) Ni
(b) Fe
(c) Pt
(d) W

Answer : D

Question. The arrangement of elements in the Modem Periodic Table is based on their
(a) increasing atomic mass in the period
(b) increasing atomic number in the horizontal rows
(c) increasing atomic number in the vertical columns
(d) increasing atomic mass in the group

Answer : B

Question. Upto which element, the Law of Octaves was found to be applicable 
(a) Oxygen
(b) Calcium
(c) Cobalt
(d) Potassium

Answer : B

Question. An atom of an element has the electronic confi-guration 2,8,2. To which group does it belong?
(a) 4th group
(b) 6th group
(c) 3rd group
(d) 2nd group

Answer : D

Question. Which one of the following elements exhibit maximum number of valence electrons ? 
(a) Na
(b) Al
(c) Si
(d) P

Answer : D

Question. Upto which element, the Law of Octaves was found applicable?
(a) Oxygen
(b) Calcium
(c) Cobalt
(d) Potassium

Answer : B

Question. What is the atomic number of element of period 3 and group 17 of the Periodic Table?
(a) 10
(b) 4
(c) 17
(d) 21

Answer : C

Question. Where would you locate the element with electronic configuration 2, 8 in the Modem Periodic Table ? 
(a) Group 8
(b) Group 2
(c) Group 18
(d) Group 10

Answer : C

Question. Which of the following is correct order of atomic size ?
(a) Cl < F < Br < I
(b) F < Cl < Br < I
(c) I < Br < Cl < F
(d) Br < I < Cl < F

Answer : B

Question Where would you locate the element with electronic configuration 2, 8 in the Modern Periodic Table?
(a) Group 8
(b) Group 2
(c) Group 18
(d) Group 10

Answer : C

Question. Which of the following gives the correct increasing order of the atomic radii of O, F and N ? 
(a) O, F, N
(b) N, F, O
(c) O, N, F
(d) F, O, N

Answer : D

Question. The lightest liquid metal is
(a) Hg
(b) Ga
(c) Cs
(d) Fr

Answer : C

Question. Which of the following hydroxides is most basic?
(a) Be(OH)₂
(b) Ba(OH)₂
(c) Ca(OH)₂
(d) Mg(OH₂

Answer : B

Question. The element with atomic number 14 is hard and forms acidic oxide and a covalent halide. To which of the following categories does the element belong ?
(a) Metal
(b) Metalloid
(c) Non-metal
(d) Left-hand side element

Answer: B

Question. Which element was not known when Mendeleev proposed his classification ?
(a) Hydrogen
(b) Sodium
(c) Calcium
(d) Germanium

Answer: C

Question. The positions of four elements A, B, C and D in the Modern Periodic Table are shown below. Which element is most likely to form an acidic oxide ? 

(a) A
(b) B
(c) C
(d) D

Answer: C

Question. The number of shells in elements of the third period is:
(a) three
(b) two
(c) four
(d) one

Answer: A

Question. The alkaline earth metal present in group 2 and period 3 of the periodic table is:
(a) sodium
(b) magnesium
(c) calcium
(d) potassium

Answer: B

Question. The period that contains only gaseous elements are:
(a) 1
(b) 2
(c) 3
(d) 4

Answer: A

Question. Elements P, Q, R and S have atomic numbers 11, 15, 17 and 18 respectively. Which of them are reactive non-metals ?
(a) P and Q
(b) P and R
(c) Q and R
(d) R and S

Answer: C

Question. Which of the given elements A, B, C, D and E with atomic number 2, 3, 7, 10 and 30 respectively belong to the same period ?
(a) A, B, C
(b) B, C, D
(c) A, D, E
(d) B, D, E

Answer: B

Question. Which pair of elements belong to the same group if elements A, B, C, D and E have atomic number 9, 11, 17, 12 and 13 respectively.
(a) A and B
(b) B and D
(c) A and C
(d) D and E

Answer: C

Question. _______ element would lose an electron easily ?
(a) Mg
(b) Na
(c) K
(d) Ca

Answer: D

Question. Which among the following elements has the largest atomic radii ?
(a) Na
(b) Mg
(c) K
(d) Ca

Answer: D

Question. The modern periodic law is given by…………
(a) Mendeleev
(b) Einstein
(c) Bohr
(d) Mosley

Answer: D

Question. How many elements were arranged by Mendeleev in his periodic table ?
(a) 98
(b) 63
(c) 42
(d) 21

Answer: B

Question. Element X forms a chloride with the formula XCl2, which is a solid with a high melting point. X would most likely be in the same group of the Periodic Table as
(a) Na
(b) Mg
(c) Al
(d) Si

Answer: B 

Question. The correct increasing order of the atomic radii of O, F and N will be:
(a) O, F, N
(b) N, F, O
(c) O, N, F
(d) F, O, N

Answer: C 

Question. Which of the following has zero electron affinity?
(a) Halogens
(b) Alkali metals
(c) Alkaline earth metals
(d) Noble gases

Answer: D

Question. The least reactive element in group 17 is…………
(a) Fluorine
(b) Chlorine
(c) Bromine
(d) Iodine

Answer: D

Question. An element X has 4 shells and 3 valence electrons.What is its period number?
(a) 3
(b) 5
(c) 6
(d) 4

Answer: D 

Question. Which one of the following property does not increase while moving down the group in the periodic table ?
(a) Atomic radius
(b) Metallic character
(c) Valence electrons
(d) Number of shells in an element

Answer: C

Question. Which of the following statements about Newland‘ slaw of octaves is correct?
(a) It was applicable to all elements.
(b) It was applicable to elements up to calcium only.
(c) Every first and seventh element had similar properties.
(d) Noble gases werediscovered that time

Answer: B

Question. According to Mendeleev’s Periodic Law, the elements were arranged in the periodic table in the order of:
(a) Increasing atomic number
(b) Decreasing atomic number
(c) Increasing atomic masses
(d) Decreasing atomic masses

Answer: C

Question. What type of oxide would Eka– aluminium form ?
(a) EO₃
(b) E₃O₂
(c) E₂O₃
(d) EO

Answer: C

Question. Consider the following statements about an element ‘X‘ with number of protons 13.*
(A) It forms amphoteric oxide.
(B) Its valency is three.
(C) The formula of its chloride is XC₃.
The correct statements (s) is/are.
(a) only (A)
(b) only (B)
(c) (A) and (C)
(d) (A), (B) and (C)

Answer: D

Question. According to Mendeleev’s Periodic Law, the elements were arranged in the periodic table in order of their:
(a) increasing atomic number
(b) decreasing atomic number
(c) increasing atomic mass
(d) decreasing atomic mass

Answer: C

Question. As we move down the group, the number of shells:
(a) increases
(b) decreases
(c) remain Same
(d) none of the above

Answer: A

Question. How many groups are there in the periodic table?
(a) 18
(b) 8
(c) 28
(d) 17

Answer: A 

Question. The law of octaves was given by ___.
(a) Mendeleev
(b) Newlands
(c) Bohr
(d) Moseley

Answer: B

Question. Which of the following alkali metals is radioactive in nature?
(a) Potassium
(b) Rubidium
(c) Caesium
(d) Francium

Answer: D

Question. The position of element in the periodic table is generally determined by its:
(a) no of valence electrons
(b) no of shells
(c) both (a) and (b)
(d) none of the above

Answer: C

Question. Non metals usually forms :
(a) acidic oxides
(b) basic oxides
(c) neutral oxides
(d) amphoteric oxides

Answer: A

Question. The pairs of elements with the following atomic numbers have the same chemical properties:
(a) 13 and 12
(b) 3 and 11
(c) 4 and 24
(d) 2 and 1

Answer: B 

Question. In Mendeleev’s periodic table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the perioidc table later.
(a) Germanium
(b) Chlorine
(c) Oxygen
(d) Silicon

Answer: A

Question. The electronic configuration of an element M is 2, 8, 4. In modern periodic table, the element M must be placed in:
(a) 4th group
(b) 2nd group
(c) 14th group
(d) 18th group

Answer: C

Question. Which group elements are called transition metals?
(a) Group number 1 to 2
(b) Group number 13 to 18
(c) Group number 3 to 12
(d) Group number 1 to 8

Answer: C

Question. Which of the following has the highest atomic size?
(a) Magnesium
(b) Sodium
(c) Sulphur
(d) Chlorine

Answer: B

 Very Short Answer Type Questions :

Question. Write the atomic numbers of two elements ‘X’ and ‘Y’ having electronic configuration 2, 8, 2 and 2, 8, 6 respectively.
Answer: Atomic number of X = 2 + 8 + 2 = 12
Atomic number of Y = 2 + 8 + 6 = 16

Question. In the Modern Periodic Table, which are the metals among the first ten elements?
Answer: Among the first ten elements H, He, Li, Be, B, C, N, O, F, Ne; Lithium (Li) and Beryllium (Be) are metals.

Question. Write two reasons responsible for late discovery of noble gases.
Answer: (a) They are inert gases.
(b) Their valency is zero.

Question. Did Dobereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
Answer: Yes, Dobereiner’s triads also exist in the columns of Newlands’ Octaves. For example, the triad formed by the elements Li, Na, and K of Dobereiner’s triads also occurred in the columns of Newlands’ octaves.

Question. In each of the following pairs, choose the atom having the bigger size:
(i) Mg (At. No.12) or Cl (At. No. 17)
(ii) Na (At. No. 11) or K (At. No. 19)
Answer: (i) Mg since atomic size decreases from left to right in a period.
(ii) K since atomic size increases on going down a group.

Question. If an element X is placed in group 14, what will be the formula and the nature of bonding of its chloride?
Answer: If an element X is placed in group 14, its chemical formula is XCl4. The nature of bonding of its chloride is covalent bonding.

Question. Besides gallium, which other elements have since been discovered that were left by Mendeleev in his Periodic Table?
Answer: Scandium and Germanium.

Question. Answer the following questions:
(i) An element X has mass number 40 and contains 21 neutrons in its atom. To which group of the periodic table does it belong?
(ii) The element X forms a compound X2Y. Suggest an element that Y might be and give reasons for your choice.
Answer: (i) Group 1 (2, 8, 8, 1).
(ii) Oxygen (X is monovalent so Y has to be divalent to form the compound X2Y)

Question. Write the name, symbol and electronic configuration of an element X whose atomic number is 11.
Answer: The element whose atomic number is 11 is sodium.
Its symbol is Na.
Electronic configuration—2, 8, 1
Valency 1

Short Answer Type Questions :

Question. From the following elements:
4Be ; 9F ; 19K ; 20Ca
(a) Select the elements having one electron in the outermost shell.
(b) Two elements of the same group.
Write the formula of the compound and mention the nature of the compound formed by the union of 19 K and element X(2, 8, 7).
Answer: (a) ‘K’ has only one electron in the outermost shell 19K: 2, 8, 8, 1
(b) Be and Ca both are the members of 2nd group. K has only one electron in its outermost shell while the element X is only one electron short from its octet. So there would be transfer of one electron from K to X. Formula of compound: KX Nature of compound: Ionic or Electrovalent.

Question. State the main aim of classifying elements. Which is the more fundamental property of elements that is used in the development of modern periodic table? Name and state the law based on this fundamental property. On which side of the periodic table one can find metals, non- metals and metalloids?
Answer: The main aim of classification is to make study of elements systematic and easy. The fundamental property of elements that is used in the development of modern periodic table is Atomic number. According to Modern Periodic law, “Physical and Chemical Properties of the elements are a periodic function of their atomic numbers”. In a periodic table, metals
are on the left and non-metals are on the right. Metalloids at the border of metals and beginning of non- metals.

Question. Na, Mg and Al are the elements of the same period of modern periodic table having one, two and three valence electrons respectively. Which of these element (i) has the largest atomic radius , (ii) is least reactive ? Justify your answer stating reason for each case.
Answer: (i) Na or Sodium. The atomic size decreases from left to right due to the increase in nuclear charge.
(ii) Al is least reactive because the tendency to lose electron decreases from, left to right.

Question. Answer the following questions:
(i) Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements?
(ii) Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?
Answer: (i) Yes, they all belong to group 1 i.e, their atoms have one electron in their outermost shell.
(ii) Both Helium (He) and Neon (Ne) have filled outermost shells.
Helium has a duplet i.e., two electrons in its K shell, while neon has an octet i.e, 8 electrons in its L shell.

Question. An atom has electronic configuration 2, 8, 7.
(i) What is the atomic number of this element?
(ii) To which of the following elements would it be chemically similar ? (Atomic numbers are given in parentheses.) N(7), F(9), P(15), Ar(18).
Answer: (i) The atomic number of this element is 17.
(ii) It would be chemically similar to F(9) with configuration as 2, 7.

Question. Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the Periodic Table. Write the electronic configuration of these two elements. Which of these will be more electronegative? Why?
Answer: 

Nitrogen is more electronegative than phosphorus, because on moving down a group, the number of shell increases and electronegativity decreases.

Question. Answer the following questions:
(i) Three elements X, Y and Z belong to 17th group but 2nd, 3rd and 4th period respectively. Number of valence electrons in Y is 7. Find the number of valence electrons in X and Z.
(ii) Na, Mg, Al and P belong to third period but are placed in first, second, thirteen and fifteenth group. Number of shells occupied in Mg is three. What is the number of occupied shells in Na, Al and P. Give reasons for your answer.
(iii) The atomic radius of three elements A, B and C of a periodic table are 186 pm, 104 pm and 143 pm respectively. Giving a reason, arrange these elements in the increasing order of atomic numbers in a period.
Answer: (i) Number of valence electrons in X and Z will be 7 because the number of electrons in the outermost shell in the elements in same group is same.
(ii) In Na, Al and P number of occupied shells are three. The reason for this is that elements with same number of occupied shells are placed in same period.
(iii) Order of atomic number of elements will be :
A < C < B. Out of three, A has largest atomic radius, then C and finally B and atomic radius decreases along a period.

Question. The elements of the second period of the Periodic Table are given below: Li, Be, B, C, N, O, F.
(i) Give reason to explain why atomic radii decrease from Li to F.
(ii) Identify the most (a) metallic and (b) non-metallic element.
Answer: (i) On moving from left to right in a period force of attraction between nucleus and electrons increases which results in decrease in size.
(ii) (a) Most metallic element is ‘Li’.
(b) Most non-metallic element is ‘F’.

Question. Answer the following questions:
(i) What are metalloids?
(ii) Name any four metalloids?
(iii) Predict which of the following elements will form cation and will form anions?
(a) Na,
(b) Al,
(c) Cl,
(d) O.
(iv) Name two elements that are inert in nature.
Answer: (i) Borderline elements which are intermediate in properties between metals and non-metals are called metalloids.
(ii) Boron, silicon, germanium and arsenic.
(iii) Na and Al are metals. They form cations.
(iv) Cl and O are non-metals. They form anions.

Question. Give an example of:
(i) A metal that is liquid at room temperature.
(ii) A non-metal that is liquid at room temperature.
(iii) An inert gas (At. No. < 20)
Answer: (i) Mercury
(ii) Bromine
(iii) Helium or Neon or Argon.

Question. Name the following elements:
(i) Three elements that have a single electron in their outermost shells.
(ii) Two elements that have two electrons in their outermost shells.
(iii) Three elements with filled outermost shells.
(iv) Name two elements you would expect to show chemical reactions similar to magnesium. What is the basis for your choice?
Answer: (i) Lithium (Li), Sodium (Na), and Potassium (K) have a single electron in their outermost shells.
(ii) Magnesium (Mg) and Calcium (Ca) have two electrons in their outermost shells.
(iii) Neon (Ne), Argon (Ar) and Xenon (Xe) have filled outermost shells.
(iv) Calcium (Ca) and strontium (Sr) are expected to show chemical reactions similar to magnesium (Mg). This is because the number of valence electrons (2) is same in all
these three elements and they belong to same group.

Question. Name any two elements of group one and write their electronic configuration. What similarity do you observe in their electronic configuration? Write the formula of oxide of any of the above said elements.
Answer: Two elements of group 1 are Sodium (11) and Potassium (19).
Electronic configuration,
Na = 2, 8, 1.; K = 2,8,8,1.
Both have one electrons in their valence shell. The formula of their oxide is: Na2O and K2O.

Question. Based on the group valency of elements write the molecular formula of the following compounds giving justification for each :
(i) Oxide of first group elements.
(ii) Halide of the elements of group thirteen, and (iii) Compound formed when an element, A of group 2 combines with an element, B of group seventeen.
Answer: (i) Sodium is a group one element (Na) so its configuration is 2, 8, 1 and its valency is 1.
Oxide has a valency of 2. So, their formula would be Formula for sodium oxide is Na2O.
(ii) Halide is any Halogen. Group 13 means for example, we take Aluminium (Al), its configuration is 2, 8, 3, valency of Al is 3, valency of Cl is 1.
So Formula would be AlCl3 (Aluminium chloride). 173
(iii) Element of group 2 for example Mg 2, 8, 2, its valency would be 2.
Element of group 17 would be Cl 2, 8, 7, valency would be 1.
Formula would be MgCl2 (Magnesium chloride).

Question. State two characteristics of groups.
Answer: All the elements in a group have the following characteristics:
(a) All element in a group show same number of valence electrons, hence show similar properties.
(b) As we move top to bottom in a group the atomic radius goes on increasing and there is a slight gradation in properties.

Question. Write all the elements present in third period of the Periodic Table and give their electronic configuration.
Answer: Elements of third period are
        Na Mg Al Si P S Cl Ar
3rd Period KLM KLM KLM KLM KLM KLM KLM KLM
2, 8, 1 2, 8, 2 2, 8, 3 2, 8, 4 2, 8, 5 2, 8, 6 2, 8, 7 2, 8, 8

Question. What happens to the valency of elements as we move from left to right in a Periodic Table?
Answer: As we move from left to right in a Periodic Table the valency first increases till 4 and then again decreases.
L → R Valency → 1 2 3 4 3 2 1 0
in a period

Question. How does electronic configuration helps us to locate the position of element in the Periodic Table?
Answer: The electronic configuration of an atom conveys the valence electrons and number of shells. Valence electrons helps in detecting the group number.
Number of shells in an atom tells the period to which it belongs.

Question. The number of electrons goes on increasing in the outer shell as we move from left to right in a period, why does the atomic size goes on decreasing?
Answer: In a period all elements have same number of shells. As we move from left to right in a period the number of electrons goes on increasing at the same time the number of protons also goes on increasing therefore attraction force of nucleus increases and pulls the valence electrons i.e. the outermost shell towards the nucleus and hence the size of atom goes on decreasing.
Size of atom decrease from L → R in a period.

Question. What happens to the metallic character as we move from top to bottom in a group?
Answer: The metallic character increases as we move from top to bottom as the tendency to lose electrons increases.

Question. Name the group number of the following elements, halogens, alkali metals, inert gases, hydrogen, in the Modern Periodic Table.
Answer: Halogens — group No. 17
Alkali metals — group No. 1
Inert gases — group No. 18
Hydrogen — group No. 1

Question. What happens to the non-metallic character as we move from top to bottom in a group?
Answer: The non-metallic character decreases as we move from top to bottom in a group as the tendency to gain electrons decreases down the group.

Q1. Why Mendeleev could not assign fixed position to hydrogen in the table?
Answer: (a) Hydrogen resembles alkali metal, i.e. like alkali metals it combines with halogen, oxygen and sulphur to form compounds with similar formula as alkalis.
(b) Like halogen, hydrogen also exists as diatomic molecule and combine with metal and non-metals to form covalent compounds.

Question. The elements of the second period of the Periodic Table are given below:
           Li    Be    B    C   N   O    F
(a) Give reason to explain why atomic radii decreases from Li to F.
(b) Identify the most
(i) Metallic and (ii) Non-metallic element. 
Answer: (a) In a period on moving from left to right, the atomic number increases, the number of shells remains the same, nuclear charge increases the force of attraction of electrons towards the centre increases. The valence electrons are pulled at the centre, hence atomic radii decreases from Li to F.
(b) (i) Most metallic element → Li
(ii) Most non-metallic element → F.

Question. The elements of the third period of the Periodic Table are given below:
Group  I   II   III  IV  V   VI  VII
          Na  Mg  Al   Si   P   S    Cl
(a) Which atom is bigger — Na or Mg? Why?
(b) Identify the most
(i) Metallic and (ii) Non-metallic element in period 3.
Answer: (a) Na atom is bigger in size this is because as we move from Na to Cl, the atomic number goes on increasing and the nuclear charge also increases. It pulls/attract the valence electrons at the centre and thus the atomic size decreases.
(b) (i) Most metallic — Na
(ii) Most non-metallic — Cl

Question. The atomic number of ‘X’ is 17. Predict its (a) valency, (b) formula of halide, (c) type of ion formed, (d) reactivity with respect to the other members of same group.
Answer: X’ has atomic number 17
∴ Electronic configuration → 2, 8, 7
(a) Valency = 1
(b) Formula of halide = HX
(c) Type of ion formed = Negative ion (Anion).
(d) Reactivity = Most reactive among those elements which lie below X in a group.

Case Based Questions :

Study the chart carefully and answer the following questions from. 

Question. Which element present in the chart has the same number of electrons as K+ and Cl– ? 
(a) C
(b) D
(c) E
(d) F

Answer: D

Question. Which formula is correct for oxide of D? 
(a) DO
(b) D2O
(c) D2O3
(d) D2O5

Answer: C

Question. Most metallic character is shown by which of the following: 
(a) D
(b) E
(c) F
(d) B

Answer: A

Question. Chloride of element E has the formula 
(a) ECl5
(b) ECl4
(c) ECl2
(d) ECl3

Answer: B

Question. Character of metalloid is shown by which of the following? 
(a) E
(b) A
(c) B
(d) C

Answer: A

Read the following information the and answer the followingquestions from.The following table shows the position of the elements A, B, C, D, E, F, G, H, I, J, K, L, M, N in the period table. 

With reference to the table, answer the following:

Question. Which elements have complete outer electronic configuration?
(a) F and J
(b) D and E
(c) E and N
(d) M and N

Answer: C

Question. Atomic size refers to the radius of an atom. The atomic size may be visualised as the distance between the centre of the nucleus and the outermost shell of an isolated atom.
Study the given graph which represents the trend of atomic size with respect to the periodic table. 

Which of the following is the correct order for atomic size?
(a) A > B > C > D > E
(b) F < G < H < I
(c) J > K > L < M > N
(d) E < F < G < H < I

Answer: A

Question. Which of the following states Modern Periodic Law?
(a) Properties of elements are the periodic function of their atomic number
(b) Properties of elements are the periodic function of their atomic size
(c) Properties of elements are the group function of their atomic number
(d) Properties of elements are the periodic function of their valency

Answer: A

Question. Which of the following reason correctly justifies that “bromine has smaller atomic radius than potassium”?
(a) Br and K are in the same group. Atomic size increases down the group.
(b) Br and K are in the same period. Atomic size increases across the period due to increase in number of shells.
(c) Br and K are in the same group. Atomic size decreases down the group.
(d) Br and K are in the same period. Atomic size decreases across the period from left to right.

Answer: D

Question. Identify the correct elements from the table.
(a) B- boron, C- Neon, M- oxygen
(b) G-aluminium, I- Chlorine, K-calcium
(c) F- sodium, K- caesium, L- Lithium
(d) B- boron, H- carbon, L- Nitrogen

Answer: B

Read the following passage carefully and answer the following questions from With the constant discovery of a large number of elements, it became necessary to classify them and arrange them according to their periodic properties. Dobereiner arranged the elements with similar properties into groups. He classified some groups of three elements having similar physical and chemical properties, called Dobereiner’s triads. John Newland’s later arranged all elements in order of increasing atomic masses and found that every eighth element has similar properties as the first one in the chart.

Question. {Cl, Br, I} is a Dobereiner’s triad. In this triad, if the atomic masses of Cl and I are 35.5 and 127 respectively, what is the atomic mass of Br?
(a) 162.5
(b) 91.5
(c) 45.625
(d) 81.25

Answer: D

Question. Which is a Dobereiner’s triad: 
(a) K, Al, Ca
(b) Li, Al, Ca
(c) Li, Na, K
(d) Li, K, Na

Answer: C

Question. Newland’s law of Octaves is obeyed by two elements A and B showing similar properties. The number of elements between A and B is: 
(a) 8
(b) 6
(c) 7
(d) 5

Answer: B

Question. Properties of Magnesium are similar to those of which element according to Newland’s law of octaves? 
(a) Beryllium
(b) Lithium
(c) Potassium
(d) Sodium

Answer: A

Question. Elements are arranged in Dobereiner’s triad on the basis of: 
(a) Atomic mass
(b) Atomic Number
(c) Number of Electrons
(d) Number of Neutrons

Answer: A

Read the following passage carefully and answer the following questions from When elements are arranged in the increasing order of their atomic numbers, we observe the recurrence of properties of the elements after certain regular intervals. This recurrence is known as periodicity. A number of physical properties such as atomic size, metallic and non-metallic character, etc. show periodic variation. Properties vary differently moving from left to right in a period and top to down in a group. Moving in a period from left to right, the number of shells remain the same but valence electron increase by one number. This results in an increase in nuclear charge. Going down in a group, the number of valence shells increases while the valence electrons remain the same. Observe some periodic table trends in the given figure.

Question. As we go down in a group in the periodic table, the electropositive character of the element
(a) Decreases
(b) Increases
(c) Changes but irregularly
(d) Remains constant

Answer: B

Question. In the second period in the table, which element has the largest size 
(a) N
(b) F
(c) Li
(d) Be

Answer: C

Question. Which of the following elements has three valence electrons? 
(a) Al
(b) S
(c) Cs
(d) Ca

Answer: A

Question. In the periodic table, the metallic character of the elements: 
(a) Increases from left to right and decreases down the group
(b) Decreases from left to right and increases down the group
(c) Increases from left to right and increases down the group
(d) Deceases from left to right and decreases down the group

Answer: B

Question. Moving along a period results in an increase of 
(a) Atomic size
(b) Number of valence electrons
(c) Electropositive character
(d) All of the above

Answer: B

Q.1 A and B are two elements having similar properties which obey Newlands law of octaves. How many elements are there in between A and B?

Q.2 Two elements X and Y have atomic number 12 and 16 respectively. Write the electronic configuration for these elements to which period of the modern periodic table does the element “X” belong? What type of bond will be formed between them and why?

Q.3 an element X (2, 8, 2) combines separately with NO3 and (SO4)2, (PO4)3 radicals. Write the formulae of the three compounds so formed. To which group of the periodic table does the element X belong? Will it form covalent or ionic compound? Why?

Q.4 X Y and Z are the elements of Dobereiners triad. If the atomic mass of X is 7 and that of Z is 39. What should be the atomic mass of Y.

Q.5 The following table shows the position of 6 elements A, B, C, D, E and F in the periodic table:

Using the above table answer the following question:

(a) Which element will form only covalent compound?

(b) Which element is a metal with valency2?

(c) Which element is a nonmetal with valence of three?

(d) Out of D and E which one has a bigger atomic radius and why?

(e) Write the common name for these family of elements C and F?

Please refer to link below for CBSE Class 10 Chemistry Hots-Periodic Classification of Elements.

Question. X, Y and Z are the elements of a dobereiners triad. If the atomic mass of x is 7 and that of z is 39, what should be the atomic mass of y?

Answer: (7 + 39) / 2 = 46/2 y = 23.

Question. A and B are the two elements having similar properties which obey Newlands law of octaves. How many elements are there in between A and B?

Answer: Six elements.

Question. Two elements X and Y have atomic numbers 12 and 16 respectively. Write the electronic configuration for these elements. To which period of the modern periodic table do these two elements belong? What type of bond will be formed between them and why?

Answer: (a) Co & Ni

(b) Li, Na , K

(c) Mn 

(d) O, S, Se