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Periodic Classification & Chemical Bonding — Homi Bhabha Class 9 Chemistry MCQs with Solutions
Free Homi Bhabha Class 9 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 · easy · theory
In the modern periodic table, the elements are arranged in order of increasing
A. atomic mass
B. density
C. number of neutrons
D. atomic number ✓ Correct
Solution: The modern periodic law arranges elements by increasing atomic number (the number of protons), which removed the few anomalies present in Mendeleev's mass-based order.
Q2 — Basics of the Periodic Table · easy · theory
The horizontal rows of the periodic table are known as periods, while the vertical columns are known as
A. blocks
B. series
C. groups ✓ Correct
D. shells
Solution: The vertical columns are called groups (there are 18 of them), and the horizontal rows are called periods.
Q3 — Electronic Configuration · easy · theory
According to the 2n squared rule, the maximum number of electrons that the second shell (L shell) can hold is
A. 2
B. 18
C. 8 ✓ Correct
D. 32
Solution: The maximum number of electrons in a shell is 2n². For the L shell n = 2, so 2 × (2)² = 8 electrons.
Q4 — Chemical Reactivity · easy · theory
Which of the following families of elements is the LEAST reactive?
A. Halogens
B. Alkaline earth metals
C. Noble gases ✓ Correct
D. Alkali metals
Solution: Noble gases (Group 18) have completely filled outermost shells, so they have almost no tendency to gain, lose or share electrons, which makes them the least reactive family.
Q5 — Chemical Reactivity · easy · theory
Metals become chemically reactive mainly by
A. keeping all their electrons unchanged
B. losing their valence electrons to form positive ions ✓ Correct
C. gaining electrons to form negative ions
D. sharing electrons equally with other metals
Solution: Metals have only a few loosely held valence electrons. They react by losing these electrons to form positive ions, which is why elements such as sodium and potassium are very reactive.
Q6 — Ionic & Covalent Compounds · easy · theory
A chemical bond formed by the complete transfer of one or more electrons from one atom to another is called
A. a covalent bond
B. an ionic (electrovalent) bond ✓ Correct
C. a metallic bond
D. a hydrogen bond
Solution: When electrons are transferred, oppositely charged ions are formed and attract each other. This electrostatic attraction between the ions is an ionic (electrovalent) bond, as in sodium chloride.
Q7 — 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.
Q8 — 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.
Q9 — 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.
Q10 — 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.
Q11 — 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.
Q12 — 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).
Q13 — 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).
Q14 — 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).
Q15 — 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.
Q16 — 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.
Q17 — 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.
Q18 — 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.
Q19 — 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.
Q20 — Basics of the Periodic Table · hard · numerical
An element belongs to Period 3 of the periodic table and its atom has 4 electrons in the outermost shell. What is the atomic number of this element?
A. 12
B. 18
C. 4
D. 14 ✓ Correct
Solution: A Period 3 atom fills the first two shells (2 + 8 = 10 electrons) and places the rest in the third shell. With 4 valence electrons the total is 2 + 8 + 4 = 14, so the atomic number is 14.
Q21 — Electronic Configuration · hard · theory
The atom of an element has 2 electrons in its K shell and 8 electrons in its L shell, with no other electrons. Which statement about this element is correct?
A. It is a metal with valency 8
B. It is a noble gas that is chemically inert with valency 0 ✓ Correct
C. It is a halogen that gains one electron
D. It is a reactive metal with valency 2
Solution: The configuration 2, 8 (10 electrons, neon) has a completely filled outermost shell. Such an atom has no tendency to gain, lose or share electrons, so it is a chemically inert noble gas with valency 0.
Q22 — Electronic Configuration · hard · theory
Two atoms P and Q have the electronic configurations 2, 8, 2 and 2, 8, 8, 2 respectively. Which conclusion is correct?
A. P and Q have completely different valencies
B. Both belong to Group 2 and show similar chemical properties ✓ Correct
C. Q is a non-metal
D. Both belong to the same period
Solution: Both atoms have 2 valence electrons, so both lie in Group 2 and behave similarly (like magnesium and calcium). Q simply has one extra shell, so it is a larger atom placed in a lower period.
Q23 — Chemical Reactivity · hard · theory
Fluorine is more reactive than chlorine, even though both are halogens that react by gaining one electron. The best reason is that
A. the fluorine atom is smaller, so its nucleus attracts an incoming electron more strongly ✓ Correct
B. fluorine loses electrons more readily than chlorine
C. fluorine has more electron shells than chlorine
D. fluorine is a metal while chlorine is a non-metal
Solution: Non-metals react by gaining electrons. The smaller fluorine atom holds an added electron closer to its nucleus, so it attracts an extra electron more strongly than the larger chlorine atom, making fluorine more reactive.
Q24 — Chemical Reactivity · hard · theory
Assertion: Noble gases normally do not take part in chemical reactions. Reason: The outermost shells of noble gas atoms are completely filled with electrons. Choose the correct option.
A. Both assertion and reason are true and the reason correctly explains the assertion ✓ Correct
B. The assertion is false but the reason is true
C. The assertion is true but the reason is false
D. Both assertion and reason are true but the reason does not explain the assertion
Solution: A completely filled outermost shell is a very stable arrangement, so noble gas atoms have no tendency to gain, lose or share electrons. The reason is therefore the correct explanation of why noble gases are unreactive.
Q25 — Ionic & Covalent Compounds · hard · theory
In a molecule of methane (CH4), each hydrogen atom is joined to the carbon atom by
A. a complete transfer of electrons (ionic bond)
B. a metallic bond
C. a shared pair of electrons (covalent bond) ✓ Correct
D. the attraction between two positive ions
Solution: Carbon and hydrogen are both non-metals that hold their electrons strongly, so instead of transferring electrons they share pairs of them. Each carbon-hydrogen link is a single covalent bond.
Q26 — Ionic & Covalent Compounds · hard · theory
Element X has the configuration 2, 8, 2 and element Y has the configuration 2, 7. What is the most likely formula of the compound formed and the type of bond?
A. XY, ionic bond
B. X2Y, covalent bond
C. XY2, covalent bond
D. XY2, ionic bond ✓ Correct
Solution: X (a metal) loses its 2 valence electrons to form X2+, and each Y (a non-metal with valency 1) gains one electron to form Y-. To balance the charges, two Y- combine with one X2+, giving the ionic compound XY2 (like magnesium fluoride).
Q27 — 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.
Q28 — 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.
Q29 — 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.
Q30 — 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.