CBSE Class 10 Chemistry Periodic Classification of Elements Worksheet Set G

PERIODIC CLASSIFICATION OF ELEMENTS

Very Short Answer type Questions

Question. Write the number of vertical columns in the modern periodic table. What are these columns called?
Answer : There are 18 vertical columns in the modern periodic table. These vertical columns are called groups.

Question. On moving from left to right in the second period when happens to the number of valence electrons?
Answer : Number of valence electrons increases from left to right in the second period.

Question. Write the number of horizontal rows in the modern periodic table. What are these rows called?
Answer : There are seven horizontal rows in the modern periodic table. These rows are called periods.

Question. How does reactivity of metals vary down a group?
Answer : Reactivity of metals goes on increasing down a group.

Question. How does atomic size vary from left to right in a period?
Answer : Atomic size decreases from left to right in a period.

Short Answer type Questions

Question. The atomic numbers of three elements, X, Y and Z are 9,11 and 17 respectively. Which two of these elements will show similar chemical properties? Why?
Answer : Electronic configuration of X, Y and Z will be:
X(9) : 2, 7
Y(11) : 2, 8, 1
Z(17) : 2, 8, 7
X and Z will show similar chemical properties due to same number of valence electrons.

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 decrease from Li to F.
(b) Identify the most
(i) metallic and
(ii) non-metallic element.
Answer : (a) It is because nuclear charge increases due to increase in atomic number, therefore, force of attraction between nucleus and valence electrons increases, i.e. effective nuclear charge increases, hence atomic radii decrease from Li to F.
(b) (i) Most metallic element is ‘Li’ as it can lose electrons easily due to larger atomic size.
(ii) Most non-metallic element is ‘F’ because it can gain electrons easily due to smallest atomic size.

Question. What were the limitations of Döbereiner’s classification?
Answer : (a) All the existing elements were not classified.
(b) Döbereiner could identify only three triads from the elements.
Hence this system was not useful.

Question. Did Döbereiner’s triads also exist in the columns of Newland’s Octaves? Compare and find out.
Answer : Yes, it exists in the Newland’s octave. It is Li, Na and K.

Question. Why do you think noble gases are placed in a separate group?
Answer : Noble gases are inactive, do not resemble other elements and all of them show same properties, hence they are grouped separately.

Question. Name:
(a) Three elements that have a single electron in their outermost shells.
(b) Two elements that have two electrons in their outermost shells.
(c) Three elements with filled outermost shells.
Answer : (a) Li, Na, K
(2, 1) (2, 8, 1) (2, 8, 8, 1)
(b) Be, Mg
(2, 2) (2, 8, 2)
(c) He, Ne, Ar
(2) (2, 8) (2, 8, 8)

Question. (a) Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements?
(b) Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?
Answer : (a) All these metals are highly reactive, they have same valence electrons i.e. 1 and can readily loose electrons to become positive ions.
(b) Helium and neon have completely filled outermost shell.

Question. Which element has
(a) two shells, both of which are completely filled with electrons?
(b) the electronic configuration 2, 8, 2?
(c) a total of three shells, with four electrons in its valence shell?
(d) a total of two shells, with three electrons in its valence shell?
(e) twice as many electrons in its second shell as in its first shell?
Answer : (a) Ne (2, 8) (b) Mg (2, 8, 2)
(c) Si (2, 8, 4) (d) B (2, 3)
(e) C (2, 4)

Question. Name two elements you would expect to show chemical reactions similar to magnesium.
What is the basis for your choice?
Answer : Calcium and barium.
Reason : (i) Both of them belong to same group as magnesium.
(ii) Ba and Ca has same valence electrons as Mg, and will show same properties as of magnesium.

Question. In the Modern Periodic Table, which are the metals among the first ten elements.
Answer : Lithium and beryllium are metals.

Question. Besides gallium, which other elements have since been discovered that were left by Mendeleev in his Periodic Table? (any two)
Answer : Besides gallium, germanium and scandium have been discovered.

Question. By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristics?
Ga, Ge, As, Se, Be
Answer : Among the given elements Be will show maximum metallic characteristics as it belongs to extreme left of the Periodic Table.

Question. What were the limitations of Newlands’ Law of Octaves?
Answer : • Newlands’ law was applicable only till calcium, after Ca, every eighth element did not possess properties similar to first.
• New elements discovered did not fit into the law.
• Wrong order of arrangement of elements was done, e.g. Co and Ni do not resemble halogen were found together in same slot, Fe being similar to Co and Ni was separated and kept in different slot.

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) Mg.

Question. How could the Modern Periodic Table remove various anomalies of Mendeleev’s Periodic Table?
Answer : Modern Periodic Table is based on the atomic number of elements, therefore
(i) problem of isotopes was solved because isotopes have same atomic number
(ii) wrong order of Ar, K, Co, Ni was removed.

Question. (a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
Answer : (a) All other elements have same valence electrons and their valency is 3.
(b) All are non-metals, they have same valence electrons i.e., 7 and their valency is
1, all of them gain electrons to form negative ions.

Question. Which of the following statements is not a correct statement about the trends when going from, left to right across the periods of the Periodic Table?
(a) The elements become less metallic in nature.
(b) The number of valence electrons increases.
(c) The atoms lose their electrons more easily.
(d) The oxides become more acidic.
Answer : (c) The atoms lose their electrons more easily.

Question. An atom has electronic configuration 2, 8, 7.
(a) What is the atomic number of this element?
(b) 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 : (a) The atomic number of the element is 17.
(b) F(9) (2, 7) will be chemically similar to the given element.

Question. What were the criteria used by Mendeleev in creating his Periodic Table?
Answer : (i) Increasing order of atomic mass of the elements.
(ii) All elements in a group with similar properties.
(iii) The formula of oxides and hydrides formed by an element.

Question. How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?
Answer : The position of element depends upon its electronic configuration. The number of shells is equal to the period number. The valence electrons decides the group number in which it will be, elements with 1 valence electrons belong to group 1.
Elements with 2 valence electrons belong to group 2.

Question. In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21 and 38. Which of these have physical and chemical properties resembling calcium.
Answer : Ca atomic number — 20
Electronic configuration — 2, 8, 8, 2
Elements with atomic number 12 → 2, 8, 2 and atomic number 38 → 2, 8, 18, 8, 2 will resemble calcium as they all have same valence electrons and their chemical properties are also same.

Question. Nitrogen (atomic number 7) and phosphorous (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 atomic number 7 → 2, 5
Phosphorus atomic number 15 → 2, 8, 5
Nitrogen with two shells will be more electronegative because it can easily gain electron due to its smaller size of atom, the nuclear charge attracts the electron easily to become negative ion.

Question. Use Mendeleev’s Periodic Table to predict the formulae for the oxides of the following elements:
K, C, Al, Si, Ba
Answer : 

Question. Compare and contrast the arrangement of elements in Mendeleev’s Periodic Table and the Modern Periodic Table.
Answer : 

Question. The position of three elements A, B and C in the Periodic Table are shown below:

(a) State whether A is a metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller in size than B?
(d) Which type of ion, cation or anion, will be formed by element A?
Answer : (a) ‘A’ is non-metal.
(b) ‘C’ is less reactive than ‘A’
(c) ‘C’ is smaller in size than ‘B’
(d) ‘A’ will form negatively charged ion — Anion

Question. How does the electronic configuration of an atom of an element relate to its position in the
Answer : The position of element depends upon number of valence electrons which depend upon electronic configuration. Those elements which have same valence electrons, occupy same group.
Those elements which have one valence electron belong to group 1.
Elements with two valence electrons belong to group 2. 
Period number is equal to number of shells.
If valence electrons are equal to 1, it belongs to group 1. If it has 2 shells, it belongs to second period, e.g. if element ‘X’ has atomic number 11, its electronic configuration is 2, 8,1. It has one valence electron, it belongs to group 1 and it has three shells therefore, it is in third period.

Question. The elements of the third period of the Periodic Table are given below:
Na, Mg, Al, Si, P,S, Cl, Ar
(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) Sodium is bigger than magnesium as it has lesser nuclear charge so there is less force of attraction between nucleus and valence electrons and less effective nuclear charge. It is, therefore, bigger in size.
(b) (i) Sodium is the most metallic as it can lose electrons easily due to its larger atomic size,
(ii) Chlorine is the most non-metallic element because it can gain electrons easily due to its smallest atomic size.

Question. How can the valency of an element be determined if its electronic configuration is known?
What will be ‘ the valency of an element of atomic number 9 (nine)?
Answer : If the element has 1, 2, 3, 4 valence electrons, its valency will be 1, 2, 3, 4 respectively.
If the element has 5, 6, 7, 8 valence electrons, its valency will be 3, 2, 1, 0. Element with atomic number 9 has electronic configuration 2, 7. So, its valency will be 1. 
modern periodic table? Explain with one example.

Question. On the basis of electronic configuration, how will you identify the first and the last element of a period?
Answer : First element has 1 valence electron and last element has 8 valence electrons. Number of shells remain the same in the same period.

Question. An element ‘X’ belongs to 3rd period and group 17 of the periodic table. State its (a) electronic configuration, (b) valency. Justify your answer with reasoning.
Answer : (a) X(17) : 2, 8, 7
(b) Valency : 1
It has atomic number 17 and therefore, electronic configuration will be 2, 8, 7. It can gain one electron to become stable therefore, its valency is equal to 1. It belongs to third period, as it has three shells. It belongs to group 17 because it has 7 valence electrons.

Question. State Mendeleev’s periodic law. Write two achievements of Mendeleev’s periodic table
Answer : Mendeleev’s Periodic Law: ‘Properties of elements are the periodic function of their atomic masses.
Achievements:
(a) It could classify all the elements discovered at that time.
(b) It helped in discovery of new elements.
(c) It helped in correction of atomic mass of somd of the elements.

Question. The formula of magnesium oxide is MgO. State the formula of barium nitrate and barium sulphate, if barium belongs to the same group as magnesium.
Answer :

Question. Choose from the following: 20^Ca, 3^Li, 11^Na, 10^Ne
(a) An element having two shells completely filled with electrons.
(b) Two elements belonging to the same group of the periodic table.
Answer : (a) 10Ne has electronic configuration 2, 8. Its both shells are completely filled.
(b) 3Li and 11Na belong to same group of periodic table, ie. 1st group.

Question. Why do all the elements of the (a) same group have similar properties, (b) same period have different properties?
Answer : (a) Elements of same group have similar properties due to same number of valence electrons, therefore, they have same valency.
(b) Elements of same period have different properties as they differ in number of valence electrons.

Question. An element ‘E’ has following electronic configuration:

(a) To which group of the periodic table does element ‘E’ belong?
(b) To which period of the periodic table does element ‘E’ belong?
(c) State the number of valence electrons present in element ‘E’.
(d) State the valency of the element ‘E’.
Answer : (a) ‘E’ belongs to group 16. (b) It belongs to 3rd period.
(c) It has 6 valence electrons. (d) Its valency is equal to 2.

Question. The electronic configuration of two elements ‘A’ and ‘B’ are 2, 8, 3 and 2, 8, 7 respectively. Find the atomic number of these elements. State the nature and formula of the compound formed by the union of these two elements.
Answer :

 Question. Write the atomic number of these elements. What will be formula of the compound formed and the nature of bond between them when these two elements chemically combine together?
Answer : ‘A’ has atomic number 17. Its electronic configuration is 2, 8, 7. Its valency is equal to 1. number
20. Its electronic configuration is 2, 8, 8, 2. Its
‘B’ has atomic valency is 2.
Ionic bond will be formed.

Question. Choose from the following: 4^Be, 9^F, 19^K, 20^Ca
(a) The element having one electron in the outermost shell.
(b) Two elements of the same group.
Answer : (a) 19^K has one valence electron.
(b) 4^Be and 20^Ca belong to the same group.

Question. The atomic number of three elements are given below:

Write the symbol of the element which belongs to (o) group 13, (b) group 15, of the periodic table. State the period of the periodic table to which these elements belong. Give reason for your answer.
Answer : (a) A belongs to group 13 because its electronic configuration is 2, 3, ie. it has 3 valence electrons.
(b) ‘B’ belongs to group 15 because its electronic configuration is 2, 5, ie. it has 5 valence electrons.
They belong to 2nd period as they ‘ both have two shells.

Question. The atomic numbers of three elements are given below:

Write the symbol of the element which belongs to (a) group 1, (b) group 14, of the periodic table. State the period of the periodic table to which these elements belong. State reason to support your answer.
Answer : (a) A belongs to group 1.
(b) B belongs to group 14.
These elements belong to second period because these elements have two shells. A has electronic 
configuration 2, 1 and has one valence electron so, belongs to group 1. ‘B’ has electronic configuration 2, 4 and has four valence electrons so, belongs to group 14 and period 2. ‘C’ has electronic configuration 2, 7 and has one valence electron. All of them contain two shells and so belong to second period.

Question. An element has atomic number 13.
(a) What is the group and period number to which this element belongs?
(b) Is this element a metal or a non- metal? Justify your answer.
Answer. (a) It belongs to group 13 and 3rd period.
(b) It is a metal because it can lose 3 electrons to become stable.

→ 1 MARK QUESTIONS

1. Mention one reason why elements should be classified?

2. Write two reasons responsible for late discovery of noble gases .

3. Chlorine, Bromine and Iodine form a Dobereiner’s triad. The atomic masses of chlorine and iodine are 35.5 and 126.9 respectively. Predict the atomic mass of bromine. (CBSE-2012)

4. Who proposed the law of octaves? Mention its one limitation.

→ 2 MARKS QUESTIONS

5. State and explain the Mendeleev’s Periodic Law and Modern Periodic Law. Also state the basis of classification for the two laws mentioned above.

6. State the merits and demerits of Mendeleev’s Periodic Law. How are the position of isotopes decided in the modern periodic table? (AI-2009)

7. What would be the nature of the oxides formed by the elements on the left hand side of the periodic table? How many valence electrons do these elements have? (CBSE-2011)

8. Based on electronic configuration, how will you identify the first and the last element of a period.

9. Lithium sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements ? (CBSE-2009)

10. What would be the nature of the oxides formed by the elements on the left hand side of the periodic table? How many valence electrons do these elements have?

→ 3 MARKS QUESTIONS

11. Part of the modern periodic table is given below:

Li (3)                Be (4)

Na (11)            Mg (12)

K (19)             Ca (20)

Rb (37)           Sr (38)

(i) Predict the number of valence electrons in Ca (20)

(ii) How many shells are present in Na (11)?

(iii) Arrange Mg, Ca, Be, Sr in increasing order of their atomic size.

(iv) Predict whether Rb is a metal or a non-metal.

(v) Out of Na, Li, Be, Mg which has the largest atomic size?

(vi) Give the electronic configuration of K

12. Give reasons:

(i) Lithium (3) and Sodium (11) are considered active metals.

(ii) Potassium (19) is more reactive than sodium (11)

(iii) Neon has zero valency.

(iv) Magnesium is a metal.

13. The position of five elements in the periodic table is given below:

(i) What is the number of valence electrons in B?

(ii) Which elements will have the smallest atomic size?

(iii) Which elements will form acidic oxides?

(iv) Which elements will form basic oxides?

(v) Which element will be the most metallic?

14. As we move horizontally from left to right, what happens:

(i) To the metallic character of elements?

(ii) To the tendency to gain electrons?

(iii) To the valency of elements?

Give reasons for your answers.

→ HOTS QUESTIONS:

15. An element X of group 15 and period 2 exists as diatomic molecule. It combines with hydrogen and forms ammonia in the presence of a suitable catalyst.

(i) Identify the element X.

(ii) Write the electronic configuration of X and count the number of valence electrons.

(iii) Draw the electron dot structure of the diatomic molecule of X and name the type of bond formed.

16. An element Y exists as yellow solid, it shows catenation and allotropy. The element Y forms two types of oxides which are also the products of thermal decomposition of ferrous sulphate. These gases are the major cause of air pollution.

(i) Write the balanced chemical equation for the thermal decomposition of ferrous sulphate.

(ii) Name the oxides which are formed by the element Y.

(iii) Identify element Y and write its electronic configuration.

(iv) Locate the position (group and period) of the element Y in the modern periodic table.

→ 17. VALUE BASED QUESTION

Government school has one teaching classes I to V all the subjects. She is able to teach only few students of same class at a time and other student keep on making noise in the class . Teachers keep on shouting in the class and often beat the students also. Some intelligent students learn very fast and even help other students of their class as well as lower classes

a) How will you compare the tendency to loose or gain electrons with the students nature.

b) Is the class like periodic table or not ? Give reasons.

c) Do you think is it possible to teach classes I to V together by one teacher ? Give one reason.

d) Give your suggestions to solve the problem.

e) Which value is possessed by students who help other students in studies ?

f) Should corporal punishment be banned in school ? Give one reason to support your answer.

Please click on below link to download CBSE Class 10 Chemistry Periodic Classification of Elements Worksheet Set G