Refer to JEE Chemistry Classification Of Elements and Periodicity In Properties MCQs Set B provided below available for download in Pdf. The MCQ Questions for Full Syllabus Chemistry with answers are aligned as per the latest syllabus and exam pattern suggested by JEE (Main), NCERT and KVS. Multiple Choice Questions for Classification Of Elements and Periodicity In Properties are an important part of exams for Full Syllabus Chemistry and if practiced properly can help you to improve your understanding and get higher marks. Refer to more Chapter-wise MCQs for JEE (Main) Full Syllabus Chemistry and also download more latest study material for all subjects
MCQ for Full Syllabus Chemistry Classification Of Elements and Periodicity In Properties
Full Syllabus Chemistry students should refer to the following multiple-choice questions with answers for Classification Of Elements and Periodicity In Properties in Full Syllabus.
Classification Of Elements and Periodicity In Properties MCQ Questions Full Syllabus Chemistry with Answers
Question: Consider the following statements:
(i) Atomic radii decreases across a row of the periodic table when we move from left to right.
(ii) Atomic radii increases down the column as we move from top to bottom.
(iii) Although the order of elements is based on atomic numbers, vertical families share similar chemical properties.
Which of the statement(s) given above is/are correct?
- a) (i), (ii) and (iii)
- b) (i) and (iii)
- c) (i) and (ii)
- d) (ii) and (iii)
Answer: (i), (ii) and (iii)
Question: Consider the following statements:
(i) Fluorine has the highest electron affinity in the periodic table.
(ii) Noble gases are placed extremely left in periodic table.
(iii) Magnesium is more metallic in nature than sodium.
Which of these statement(s) is/are correct ?
- a) Only (i)
- b) (i) and (ii)
- c) (i) and (iii)
- d) Only (ii)
Answer: Only (i)
Question: Which of the following statement(s) is/are incorrect?
(i) Ionization enthalpy is expressed in units of kJmol–1.
(ii) Ionization enthalpy is always positive.
(iii) Second ionization enthalpy will be higher than the third ionization enthalpy.
- a) Only (iii)
- b) None of these
- c) Only (ii)
- d) (ii) and (iii)
Answer: Only (iii)
Question: Consider the following statements:
(i) There are 16 groups and 7 periods in the modern periodic table.
(ii) Electro-positive character decreases on moving down a group.
(iii) Electro-negativity in a period increases right from the alkali metal to the inert gas element.
Which of these statement(s) is/are correct ?
- a) All are incorrect
- b) (i) and (iii)
- c) (i) and (ii)
- d) All are correct
Answer: All are incorrect
Question: Read the following three statements and choose the correct option. Here T stands for true and F stands for false statement.
(i) Boron has a smaller first ionization enthalpy than beryllium.
(ii) Nitrogen has smaller first ionization enthalpy than oxygen.
(iii) The first ionization enthalpy increases across a period.
- a) TFT
- b) FFT
- c) FTT
- d) TFF
Answer: TFT
Question: Consider the following statements
(i) The radius of an anion is larger than that of the parent atom.
(ii) The ionization energy generally increases with increasing atomic number in a period.
(iii) The electronegativity of elements increases on moving down across a group.
Which of the above statements is/are correct?
- a) (i) and (ii)
- b) (i) alone
- c) (ii) alone
- d) (ii) and (iii)
Answer: (i) and (ii)
Question: Match the Column-I and Column-II and select correct nswer by given code
- a) A – (r), B – (q), C – (p)
- b) A – (q), B – (r), C – (p)
- c) A – (r), B – (p), C – (q)
- d) A – (q), B – (p), C – (r)
Answer: A – (r), B – (q), C – (p)
Question:
- a) A–(t); B–(r); C–(s); D–(p); E – (q)
- b) A–(t); B–(s); C–(r); D–(p); E–(q)
- c) A–(t); B–(r); C–(s); D–(q); E – (p)
- d) A–(r); B–(t); C–(s); D–(p); E – (q)
Answer: A–(t); B–(r); C–(s); D–(p); E – (q)
Question:
- a) A – (q), B – (s), C – (p), D – (r)
- b) A – (q), B – (p), C – (s), D – (r)
- c) A – (r), B – (s), C – (r), D – (p)
- d) A – (p), B – (q), C – (s), D – (r)
Answer: A – (q), B – (s), C – (p), D – (r)
Question:
- a) A – (r), B – (p), C – (s), D – (q)
- b) A – (s), B – (p), C – (r), D – (q)
- c) A – (r), B – (s), C – (p), D – (q)
- d) None of these
Answer: A – (r), B – (p), C – (s), D – (q)
Question:
- a) A – (p), B – (s), C – (r), D – (q), E – (t)
- b) A – (s), B – (p). C – (r), D – (q), E – (t)
- c) A – (p), B–(s), C – (q), D – (r), E – (t)
- d) A – (p), B – (s), C – (r), D – (t), E – (q)
Answer: A – (p), B – (s), C – (r), D – (q), E – (t)
Question:
- a) A – (s), B – (p), C – (q), D – (r), E – (t)
- b) A – (p), B – (s), C – (q), D – (r), E – (t)
- c) A – (s), B – (q), C – (p), D – (r), E – (t)
- d) A – (s), B – (p), C – (q), D – (t), E – (r)
Answer: A – (s), B – (p), C – (q), D – (r), E – (t)
Question:
- a) A – (q), B – (s), C – (p), D – (r)
- b) A – (q), B – (p), C – (s), D – (r)
- c) A – (q), B – (s), C – (r), D – (p)
- d) A – (s), B – (q), C – (p), D – (r)
Answer: A – (q), B – (s), C – (p), D – (r)
Question:
- a) A – (s), B – (p), C – (q), D – (r), E – (t)
- b) A – (s), B – (q), C – (p), D – (r), E – (t)
- c) A – (p), B – (s), C – (q), D – (r), E – (t)
- d) A – (s), B – (p), C – (q), D – (t), E – (r)
Answer: A – (s), B – (p), C – (q), D – (r), E – (t)
More Questions..................................
Question:
- a) A – (q), B – (r), C – (s), D – (t), E – (p)
- b) A – (q), B – (s), C – (r), D – (t), E – (q)
- c) A – (r), B – (q), C – (s), D – (t), E – (p)
- d) A – (q), B – (r), C – (s), D – (p), E – (t)
Answer: A – (q), B – (r), C – (s), D – (t), E – (p)
Question:
- a) A – (s), B – (p), C – (q), D – (r)
- b) A – (s), B – (p), C – (r), D – (q)
- c) A – (p), B – (s), C – (q), D – (r)
- d) A – (s), B – (q), C – (r), D – (p)
Answer: A – (s), B – (p), C – (q), D – (r)
Question:
- a) A – (q), B – (s), C – (p), D – (r)
- b) A – (q), B – (s), C – (r), D – (p)
- c) A – (s), B – (q), C – (r), D – (p)
- d) A – (s), B – (q), C – (p), D – (r)
Answer: A – (q), B – (s), C – (p), D – (r)
Question:
- a) (A) – (s), B – (q), C – (r)
- b) (A) – (s), B – (r), C – (p)
- c) (A) – (s), B – (q), C – (p)
- d) (A) – (q), B – (s), C – (p)
Answer: (A) – (s), B – (q), C – (r)
Question:
- a) A – (t), B – (r), C – (s), D – (q), E – (p)
- b) A – (s), B – (q), C – (t), D – (r), E – (p)
- c) A – (q), B – (r), C– (t), D – (s), E – (p)
- d) A – (r), B – (q), C – (s), D – (p), E – (t)
Answer: A – (t), B – (r), C – (s), D – (q), E – (p)
Question:
Assertion : In a triad, the three elements present have same gaps of atomic masses.
Reason : Elements in a triad have similar properties
- a) Assertion is incorrect, reason is correct.
- b) Assertion is correct, reason is incorrect
- c) Assertion is correct, reason is correct; reason is not a correct explanation for assertio
- d) Assertion is correct, reason is correct; reason is a correct explanation for assertion
Answer: Assertion is incorrect, reason is correct.
Question:
Assertion : According to Mendeleev, periodic properties of elements is a function of their atomic number.
Reason : Atomic number is equal to the number of protons.
- a) Assertion is incorrect, reason is correct
- b) Assertion is correct, reason is incorrect
- c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
- d) Assertion is correct, reason is correct; reason is a correct explanation for assertion
Answer: Assertion is incorrect, reason is correct
Question:
Assertion : Atomic number of the element ununbium is 112.
Reason : Name for digits 1 and 2 is un- and bi-respectively in latin words.
- a) Assertion is correct, reason is correct; reason is a correct explanation for assertion
- b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
- c) Assertion is correct, reason is incorrect
- d) Assertion is incorrect, reason is correct.
Answer: Assertion is correct, reason is correct; reason is a correct explanation for assertion
Question:
Assertion : Second period consists of 8 elements.
Reason : Number of elements in each period is four times the number of atomic orbitals available in the energy level that is being filled.
- a) Assertion is correct, reason is incorrect
- b) Assertion is incorrect, reason is correct
- c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
- d) Assertion is correct, reason is correct; reason is a correct explanation for assertion
Answer: Assertion is correct, reason is incorrect
Question:
Assertion : Helium is placed in group 18 along with p-block elements.
Reason : It shows properties similar to p-block elements
- a) Assertion is correct, reason is incorrect
- b) Assertion is incorrect, reason is correct
- c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
- d) Assertion is correct, reason is correct; reason is a correct explanation for assertion
Answer: Assertion is correct, reason is incorrect
Question:
Assertion : Hydrogen can be placed in group 1.
Reason : Hydrogen can gain an electron to achieve a noble gas arrangement.
- a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
- b) Assertion is correct, reason is incorrect
- c) Assertion is incorrect, reason is correct
- d) Assertion is correct, reason is correct; reason is a correct explanation for assertion
Answer: Assertion is correct, reason is correct; reason is not a correct explanation for assertion
Question:
Assertion : Atomic size increases along a period.
Reason : Effective nuclear charge increases as the atomic number increases resulting in the increased attraction of electrons to the nucleus.
- a) Assertion is correct, reason is incorrect
- b) Assertion is incorrect, reason is correct
- c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
- d) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
Answer: Assertion is correct, reason is incorrect
Question:
Assertion : Second ionization enthalpy will be higher the first ionization enthalpy.
Reason : Ionization enthalpy is a quantitative measure of the tendency of an element to lose electron.
- a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
- b) Assertion is correct, reason is incorrect
- c) Assertion is incorrect, reason is correct
- d) Assertion is correct, reason is correct; reason is a correct explanation for assertion
Answer: Assertion is correct, reason is correct; reason is not a correct explanation for assertion
Question:
Assertion : Alkali metals have least value of ionization energy within a period.
Reason : They precede alkaline earth metals in periodic table.
- a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
- b) Assertion is correct, reason is incorrect
- c) Assertion is incorrect, reason is correct
- d) Assertion is correct, reason is correct; reason is a correct explanation for assertion
Answer: Assertion is correct, reason is correct; reason is not a correct explanation for assertion
Question:
Assertion : Electron gain enthalpy can be exothermic or endothermic.
Reason : Electron gain enthalpy provides a measure of the ease with which an atom adds an electron to form anion.
- a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
- b) Assertion is correct, reason is incorrect
- c) Assertion is incorrect, reason is correct
- d) Assertion is correct, reason is correct; reason is a correct explanation for assertion
Answer: Assertion is correct, reason is correct; reason is not a correct explanation for assertion
Question:
Assertion : Smaller the size of an atom greater is the electronegativity.
Reason : Electronegativity refers to the tendency of atom so share electrons with other atom
- a) Assertion is correct, reason is incorrect
- b) Assertion is incorrect, reason is correct
- c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
- d) Assertion is correct, reason is correct; reason is a correct explanation for assertion
Answer: Assertion is correct, reason is incorrect
Question: Which fact is not valid for Dobereiner's triads?
- a) The properties of middle element is roughly average of the other two elements
- b) The elements of triads belong to the same group of modern periodic table
- c) The elements of triads have same valency electrons
- d) The atomic weight of middle element is roughly average of the other two elements
Answer: The properties of middle element is roughly average of the other two elements
Question: In the Mendeleev periodic table, which of the following element instead of having lower atomic weight was placed after the element of higher atomic weight thereby ignoring the order of increasing atomic weights.
- a) Iodine
- b) Bromine
- c) Antimony
- d) Molybdenum
Answer: Iodine
Question: Which of the following is correct about Eka-Aluminium and Eka-Silicon ?
- a) Both
- b) Melting point of Eka-Aluminium is lower than the melting point of Eka-Silicon
- c) Oxides of Eka-Aluminium is Al2O3 and Eka-Silicon is Si2O3
- d) None of these
Answer: Both
Question: Which of the following elements are found in pitch blende?
- a) Both
- b) Actinium and protoactinium
- c) Neptunium and plutonium
- d) None of these
Answer: Both
Question: Which of the following period contain most of the manmade radioactive elements?
- a) Seventh
- b) Sixth
- c) Fifth
- d) None of these
Answer: Seventh
Question:
- a) 33
- b) 36
- c) 34
- d) 49
Answer: 33
Question: Which of the following elements show the given properties?
(i) All elements are metals.
(ii) Most of the elements form coloured ions, exhibit variable valence and paramagnetism.
(iii) Oftently used as catalysts.
- a) Transition elements
- b) Chalcogens
- c) Inner transition elements
- d) Representative elements
Answer: Transition elements
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) B, C, D
- b) B, D, E
- c) A, B, C
- d) A, D, E
Answer: B, C, D
Question:
- a) Both
- b) Alkali metals
- c) Halogens
- d) None of these
Answer: Both
Question: Which of the following statements is incorrect from the point of view of modern periodic table ?
- a) Noble gases are arbitrarily placed in eighteenth group
- b) Transition elements fit in the middle of long periods
- c) There are eighteen vertical columns called groups
- d) Elements are arranged in the order of increasing atomic number
Answer: Noble gases are arbitrarily placed in eighteenth group
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) Mg
- b) Si
- c) Na
- d) Al
Answer: Mg
Question: An element X belongs to fourth period and fifteenth group of the periodic table. Which one of the following is true regarding the outer electronic configuration of X ? It has
- a) Completely filled s-orbital and half-filled p-orbitals
- b) Half-filled d-robitals and completely filled s-orbitals
- c) Partially filled d-orbitals and completely filled s-orbitals
- d) None of these
Answer: Completely filled s-orbital and half-filled p-orbitals
Question:
- a) Period = 3rd, block = p, group = 16
- b) Period = 5th, block = s, group = 1
- c) Period = 3rd, block = p, group = 10
- d) Period = 4th, block = d, group = 12
Answer: Period = 3rd, block = p, group = 16
Question: The periodic table of elements does not
- a) tell us about the arrangement of atoms in a molecule
- b) include the inert gases
- c) allow us to make accurate guess of the properties of undiscovered elements
- d) reveal regularities in the occurance of elements with similar properties
Answer: tell us about the arrangement of atoms in a molecule
Question: The lightest liquid metal is
- a) Cs
- b) Hg
- c) Ga
- d) Fr
Answer: Cs
Question: The correct sequence which shows decreasing order of the ionic radii of the elements is
- a)
- b)
- c)
- d)
Answer:
Question: The ionic radii (Å) of C 4– and O2– respectively are 2.60 and 1.40. The ionic radius of the isoelectronic ion N3– would be
- a) 1.71
- b) 0.95
- c) 2.6
- d) 1.4
Answer: 1.71
Question: Which of the following species will have the smallest and the largest size?
- a)
- b)
- c)
- d)
Answer:
Question: Covalent radii of atoms varies in range of 72 pm to 133 pm from F to I while that of noble gases He to Xe varies from 120pm to 220pm. This is because in case of noble gases
- a) van der Waal radius is considered
- b) metallic radii is considered
- c) None of these
- d) covalent radius is very large
Answer: van der Waal radius is considered
Question: The van der Waal and covalent radii of fluorine atom respectively from the following figure are
- a) 147pm, 72pm
- b) 219pm, 72pm
- c) 75pm, 72pm
- d) 147pm, 144pm
Answer: 147pm, 72pm
Question:
- a)
- b)
- c)
- d) None of these
Answer:
Question:
- a) II and V
- b) I and V
- c) V and II
- d) IV and V
Answer: II and V
Question: Among the following transition elements, pick out the element/elements with highest second ionization energy.
(A) V (At. no = 23) (B) Cr (At. no = 24)
(C) Mn (At. no = 25) (D) Cu (At. no = 29)
(E) Zn (At. no = 30)
- a) (B) and (D)
- b) Only (D)
- c) (A) and (C)
- d) (B) and (E)
Answer: (B) and (D)
Question: As we move across the second period from C to F ionisation enthalpy increases but the trend from C to F for ionisation enthalpy is C < O < N < F why it is not C < N < O < F. This is because
- a) electronic configuration of N is more stable than electronic configuration of O
- b) atomic radii of N > atomic radii of O
- c) None of these
- d) atomic radii of O > atomic radii of N
Answer: electronic configuration of N is more stable than electronic configuration of O
Question: If ionisation enthalpy of oxygen is lesser than nitrogen because of two of the four 2p– electrons occupy same 2porbital than why such case is not possible with fluorine which contain greater no of paired electrons because
- a) nuclear charge overpower electronic repulsions
- b) None of these
- c) smaller size of orbitals
- d) greater size of atomic orbitals
Answer: nuclear charge overpower electronic repulsions
Question: Which of the following statements is wrong ?
- a) All isoelectronic ions belong to same period of the periodic table
- b) van der Waal’s radius of iodine is more than its covalent radius
- c) Both
- d) None of these
Answer: All isoelectronic ions belong to same period of the periodic table
Question: Which one of the following statements is incorrect ?
- a) Electron affinity decreases from fluorine to iodine in 17th group
- b) Chlorine has highest electron affinity
- c) Nitrogen has zero electron affinity
- d) Greater the nuclear charge, greater is the electron affinity
Answer: Electron affinity decreases from fluorine to iodine in 17th group
Question: The elements with zero electron affinity are
- a) Beryllium and Helium
- b) Boron and Carbon
- c) Lithium and Sodium
- d) Fluorine and Chlorine
Answer: Beryllium and Helium
Question: Which of the following property of element is directly related to electronegativity?
- a) Non-metallic character
- b) Atomic radius
- c) Ionization enthalpy
- d) None of these
Answer: Non-metallic character
Question: Which is not the correct order for the stated property.
- a) F > O > N ; first ionization enthalpy
- b) Ba > Sr > Mg ; atomic radius
- c) Cl > F > I ; electron affinity
- d) O > Se > Te ; electronegativity
Answer: F > O > N ; first ionization enthalpy
Question: In which of the following arrangements, the order is NOT according to the property indicated against it?
- a) B < C < N < O
Increasing first ionization enthalpy
- b) I < Br < F < Cl :
Increasing electron gain enthalpy
(with negative sign) - c) Li < Na < K < Rb :
Increasing metallic radius
- d) None of these
Answer: B < C < N < O
Increasing first ionization enthalpy
Question: The compounds of the s-block elements, with the exception of lithium and ...X... are predominantly ionic. Here, X refers to
- a) beryllium
- b) helium
- c) hydrogen
- d) magnesium
Answer: beryllium
Question:
- a)
- b)
- c) Both
- d) None of these
Answer:
Question: Observe the following periodic table
- a) Z > Y > X
- b) X > Z > Y
- c) Y > Z > X
- d) X > Y > Z
Answer: Z > Y > X
Question:
- a) (i) and (ii)
- b) (i) and (iii)
- c) (i), (ii) and (iii)
- d) (ii) and (iii)
Answer: (i) and (ii)
JEE Chemistry Alcohols Phenols and Ethers MCQs Set A |
JEE Chemistry Alcohols Phenols and Ethers MCQs Set B |
JEE Chemistry Alcohols Phenols and Ethers MCQs Set C |
JEE Chemistry Biomolecules MCQs Set A |
JEE Chemistry Biomolecules MCQs Set B |
JEE Chemistry Biomolecules MCQs Set C |
JEE Chemistry Carbon And Its Compounds MCQs A |
JEE Chemistry Carbon And Its Compounds MCQs B |
JEE Chemistry Carbon And Its Compounds MCQs C |
JEE Chemistry Chemical Kinetics MCQs Set A |
JEE Chemistry Chemical Kinetics MCQs Set B |
JEE Chemistry Chemistry In Everyday Life MCQs Set A |
JEE Chemistry Chemistry In Everyday Life MCQs Set B |
JEE Chemistry Classification Of Elements and Periodicity In Properties MCQs Set A |
JEE Chemistry Classification Of Elements and Periodicity In Properties MCQs Set B |
JEE Chemistry Coordination Compounds MCQs Set A |
JEE Chemistry Coordination Compounds MCQs Set B |
JEE Chemistry Coordination Compounds MCQs Set C |
JEE Chemistry Equilibrium MCQs Set A |
JEE Chemistry Equilibrium MCQs Set B |
JEE Chemistry Equilibrium MCQs Set C |
JEE Chemistry General Principles and Processes Of Isolation Of Elements MCQs Set A |
JEE Chemistry General Principles and Processes Of Isolation Of Elements MCQs Set B |
JEE Chemistry Haloalkanes and Haloarenes MCQs Set A |
JEE Chemistry Haloalkanes and Haloarenes MCQs Set B |
JEE Chemistry Hydrocarbons MCQs Set A |
JEE Chemistry Hydrocarbons MCQs Set B |
JEE Chemistry Hydrocarbons MCQs Set C |
JEE Chemistry Solutions MCQs Set A |
JEE Chemistry Solutions MCQs Set B |
JEE Chemistry Solutions MCQs Set C |
JEE Chemistry Some Basic Concepts Of Chemistry MCQs Set A |
JEE Chemistry Some Basic Concepts Of Chemistry MCQs Set B |
JEE Chemistry Structure of Atoms MCQs A |
JEE Chemistry Structure of Atoms MCQs B |
JEE Chemistry Structure of Atoms MCQs C |
JEE Chemistry Surface Chemistry MCQs Set A |
JEE Chemistry Surface Chemistry MCQs Set B |
JEE Chemistry Surface Chemistry MCQs Set C |
JEE Chemistry The D and F Block Elements MCQs Set A |
JEE Chemistry The D and F Block Elements MCQs Set B |
JEE Chemistry The D and F Block Elements MCQs Set C |
MCQs for Classification Of Elements and Periodicity In Properties Chemistry Full Syllabus
Expert teachers of studiestoday have referred to NCERT book for Full Syllabus Chemistry to develop the Chemistry Full Syllabus MCQs. If you download MCQs with answers for the above chapter you will get higher and better marks in Full Syllabus test and exams in the current year as you will be able to have stronger understanding of all concepts. Daily Multiple Choice Questions practice of Chemistry will help students to have stronger understanding of all concepts and also make them expert on all critical topics. After solving the questions given in the MCQs which have been developed as per latest books also refer to the NCERT solutions for Full Syllabus Chemistry. We have also provided lot of MCQ questions for Full Syllabus Chemistry so that you can solve questions relating to all topics given in each chapter. After solving these you should also refer to Full Syllabus Chemistry MCQ Test for the same chapter.
You can download the JEE (Main) MCQs for Full Syllabus Chemistry Classification Of Elements and Periodicity In Properties for latest session from StudiesToday.com
Yes, the MCQs issued by JEE (Main) for Full Syllabus Chemistry Classification Of Elements and Periodicity In Properties have been made available here for latest academic session
You can find JEE (Main) Full Syllabus Chemistry Classification Of Elements and Periodicity In Properties MCQs on educational websites like studiestoday.com, online tutoring platforms, and in sample question papers provided on this website.
To prepare for Classification Of Elements and Periodicity In Properties MCQs, refer to the concepts links provided by our teachers and download sample papers for free.
Yes, there are many online resources that we have provided on studiestoday.com available such as practice worksheets, question papers, and online tests for learning MCQs for Full Syllabus Chemistry Classification Of Elements and Periodicity In Properties