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Periodic Classification & Chemical Bonding — Homi Bhabha Exam Chemistry MCQs with Solutions
Free Homi Bhabha Exam Chemistry Periodic Classification & Chemical Bonding MCQs with step-by-step solutions covering Basics of the Periodic Table, Electronic Configuration, Chemical Reactivity, Ionic & Covalent Compounds. Practise online on Prepizo — no login needed.
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Sample questions with solutions
Q1 — Basics of the Periodic Table · hard · theory
The modern periodic table arranges elements in order of increasing:
A. atomic mass
B. atomic number ✓ Correct
C. density
D. number of neutrons
Solution: Moseley showed atomic number is the fundamental property, so the modern table is arranged by it.
Q2 — Basics of the Periodic Table · hard · theory
The elements of Group 1 (except hydrogen) are called:
A. noble gases
B. alkali metals ✓ Correct
C. alkaline earth metals
D. halogens
Solution: Group 1 metals (Li, Na, K, …) are the highly reactive alkali metals.
Q3 — Basics of the Periodic Table · hard · theory
The very unreactive elements placed in Group 18 are the:
A. noble (inert) gases ✓ Correct
B. transition metals
C. alkali metals
D. halogens
Solution: Group 18 contains the noble gases (He, Ne, Ar, …) which have complete outer shells.
Q4 — Electronic Configuration · hard · theory
The electronic configuration of a sodium atom (atomic number 11) is:
A. 2, 9
B. 2, 8, 1 ✓ Correct
C. 2, 8, 8
D. 8, 2, 1
Solution: Filling shells: 2 in K, 8 in L, 1 in M gives 2, 8, 1.
Q5 — Electronic Configuration · hard · numerical
The number of valence electrons in a chlorine atom (configuration 2, 8, 7) is:
A. 8
B. 2
C. 17
D. 7 ✓ Correct
Solution: The outermost shell has 7 electrons, so chlorine has 7 valence electrons.
Q6 — Electronic Configuration · hard · theory
An atom is chemically stable when its outermost shell contains ______ electrons (octet), except for the first shell which needs 2:
A. 4
B. 18
C. 2
D. 8 ✓ Correct
Solution: A complete octet (8 electrons) in the outer shell gives special stability (duplet for the first shell).
Q7 — Chemical Reactivity · hard · theory
An atom with only 1 electron in its outermost shell is:
A. a noble gas
B. a reactive metal that easily loses that electron ✓ Correct
C. chemically inert
D. a reactive non-metal that gains electrons
Solution: Losing the single valence electron gives a stable octet, so such atoms are reactive metals (e.g. Na).
Q8 — Chemical Reactivity · hard · theory
An atom with 7 electrons in its outermost shell tends to:
A. lose 7 electrons
B. gain 1 electron and act as a reactive non-metal ✓ Correct
C. lose 1 electron
D. stay inert
Solution: Gaining one electron completes the octet, so such atoms are reactive non-metals (e.g. Cl).
Q9 — Chemical Reactivity · hard · theory
As we move down Group 1 (alkali metals), the chemical reactivity:
A. becomes zero
B. increases ✓ Correct
C. remains the same
D. decreases
Solution: Down the group the valence electron is farther from the nucleus and lost more easily, so reactivity increases.
Q10 — Chemical Reactivity · hard · theory
Atoms take part in chemical reactions mainly to achieve:
A. radioactivity
B. a stable noble-gas electronic configuration ✓ Correct
C. more neutrons
D. a higher atomic mass
Solution: Atoms react to complete their outer shell and reach the stable configuration of the nearest noble gas.
Q11 — Ionic & Covalent Compounds · hard · theory
Ionic compounds conduct electricity when:
A. they are dry crystals
B. in the solid state
C. molten or dissolved in water ✓ Correct
D. they are gases
Solution: In molten or aqueous form the ions become free to move and carry current; solid ionic compounds do not conduct.
Q12 — Ionic & Covalent Compounds · hard · theory
Compared with covalent compounds, ionic compounds generally have:
A. the same melting points
B. lower melting points
C. higher melting and boiling points ✓ Correct
D. no melting point
Solution: Strong electrostatic forces between ions give ionic compounds high melting and boiling points.
Q13 — Ionic & Covalent Compounds · hard · theory
When sodium reacts with chlorine, sodium becomes ______ and chlorine becomes ______:
A. Na⁺; Cl⁺
B. Na⁻; Cl⁻
C. Na⁺ (loses 1 electron); Cl⁻ (gains 1 electron) ✓ Correct
D. Na⁻; Cl⁺
Solution: Sodium loses one electron to form Na⁺ and chlorine gains it to form Cl⁻, giving NaCl.
Q14 — Basics of the Periodic Table · medium · theory
Mendeleev arranged the elements in his periodic table in order of increasing:
A. valency
B. density
C. atomic number
D. atomic mass ✓ Correct
Solution: Mendeleev's classification was based on increasing atomic mass and similarity of properties.
Q15 — Basics of the Periodic Table · medium · theory
The horizontal rows of the periodic table are called:
A. groups
B. periods ✓ Correct
C. families
D. shells
Solution: Horizontal rows are periods; vertical columns are groups.
Q16 — Basics of the Periodic Table · medium · theory
The vertical columns of the periodic table are called:
A. periods
B. groups ✓ Correct
C. orbits
D. blocks
Solution: Vertical columns are groups; elements in a group have similar properties.
Q17 — Basics of the Periodic Table · medium · theory
The modern periodic table has ______ periods and ______ groups:
A. 18 periods and 7 groups
B. 8 periods and 8 groups
C. 7 periods and 18 groups ✓ Correct
D. 7 periods and 8 groups
Solution: There are 7 periods (rows) and 18 groups (columns) in the modern periodic table.
Q18 — Basics of the Periodic Table · medium · theory
The elements of Group 17, such as fluorine and chlorine, are called:
A. metalloids
B. noble gases
C. halogens ✓ Correct
D. alkali metals
Solution: Group 17 elements are the halogens, which are reactive non-metals.
Q19 — Electronic Configuration · medium · numerical
The maximum number of electrons that the first shell (K) of an atom can hold is:
A. 2 ✓ Correct
B. 1
C. 8
D. 18
Solution: By the $2n^2$ rule, the K shell ($n=1$) holds $2 \times 1^2 = 2$ electrons.
Q20 — Electronic Configuration · medium · numerical
The maximum number of electrons in the second shell (L) is:
A. 32
B. 8 ✓ Correct
C. 2
D. 18
Solution: For $n=2$, maximum $= 2 \times 2^2 = 8$ electrons.
Q21 — Electronic Configuration · medium · theory
The electrons present in the outermost shell of an atom are called:
A. core electrons
B. nucleons
C. valence electrons ✓ Correct
D. free electrons
Solution: Outer-shell electrons are valence electrons and decide chemical behaviour.
Q22 — Electronic Configuration · medium · theory
An element with the electronic configuration 2, 8, 8 is:
A. hydrogen
B. a noble gas (argon) ✓ Correct
C. a reactive metal
D. a halogen
Solution: The complete outer octet (2, 8, 8) is that of the noble gas argon (atomic number 18).
Q23 — Chemical Reactivity · medium · theory
Noble gases are chemically unreactive because their outermost shells are:
A. empty
B. completely filled (stable octet/duplet) ✓ Correct
C. always losing electrons
D. half filled
Solution: A complete outer shell makes noble gases stable, so they rarely react.
Q24 — Chemical Reactivity · medium · theory
The chemical reactivity of an element is mainly decided by the number of:
A. protons in the nucleus
B. neutrons
C. shells only
D. valence electrons ✓ Correct
Solution: Valence (outer-shell) electrons determine how an atom bonds and reacts.
Q25 — Chemical Reactivity · medium · theory
When a metal reacts, it usually ______ electrons, and when a non-metal reacts, it usually ______ electrons:
A. gains; loses
B. shares; loses
C. loses; shares
D. loses; gains ✓ Correct
Solution: Metals tend to lose valence electrons (forming cations); non-metals tend to gain them (forming anions).
Q26 — Ionic & Covalent Compounds · medium · theory
An ionic (electrovalent) bond is formed by the:
A. transfer of neutrons
B. transfer of electrons from one atom to another ✓ Correct
C. sharing of electrons
D. sharing of protons
Solution: In ionic bonding one atom donates electrons to another, forming oppositely charged ions that attract.
Q27 — Ionic & Covalent Compounds · medium · theory
A covalent bond is formed by the:
A. gain of neutrons
B. sharing of electrons between atoms ✓ Correct
C. loss of protons
D. complete transfer of electrons
Solution: Covalent bonds involve atoms sharing pairs of electrons.
Q28 — Ionic & Covalent Compounds · medium · theory
Sodium chloride (common salt) is an example of a(n):
A. noble gas
B. ionic compound ✓ Correct
C. metallic element
D. covalent compound
Solution: NaCl is formed by transfer of an electron from Na to Cl — an ionic compound.
Q29 — Ionic & Covalent Compounds · medium · theory
Which of the following is a covalent compound?
A. Sodium chloride (NaCl)
B. Calcium chloride (CaCl₂)
C. Magnesium oxide (MgO)
D. Water (H₂O) ✓ Correct
Solution: Water is formed by sharing electrons (covalent); the others are ionic.
Q30 — Ionic & Covalent Compounds · medium · theory
A positively charged ion formed when an atom loses electrons is called a:
A. anion
B. molecule
C. isotope
D. cation ✓ Correct
Solution: Loss of electrons leaves an excess positive charge, forming a cation (e.g. Na⁺).