Isotopes of an element have: MCQ with Answer and Explanation

Isotopes of an element have:
A. Same physical properties
B. Same mass number, different atomic number
C. Same atomic number, different mass number
D. Same number of neutrons
Answer: Option C
Solution (By JKSSB Mock Tests)
Isotopes are atoms of the same element (same atomic number, same number of protons) but different mass numbers due to varying number of neutrons. For example, ¹²C, ¹³C, ¹⁴C. Their chemical properties are similar but physical properties (mass, density, rate of diffusion) differ. Isobars have same mass number but different atomic numbers.

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Practice More chemistry Questions

Question #1
Electrovalency is the number of electrons lost or gained by an atom. The electrovalency of magnesium in MgCl₂ is:
A. 2
B. 1
C. 4
D. 6

Correct Answer: Option A


Explanation:
Magnesium loses two electrons to achieve noble gas configuration (Mg → Mg²⁺), so its electrovalency is +2. In MgCl₂, Mg²⁺ and two Cl⁻. Electrovalency is the charge on the ion. Covalency is number of covalent bonds. For Group 2 metals, electrovalency is always +2 (loss of 2 electrons).

This question belongs to: Science chemistry
Question #2
Which of the following is an allotropic form of carbon used in lead pencils?
A. Fullerene
B. Diamond
C. Graphite
D. Charcoal

Correct Answer: Option C


Explanation:
Graphite mixed with clay forms pencil 'lead'. Its layered structure marks paper. Diamond is used in cutting, fullerene in nanotechnology, charcoal in filters and fuel.

This question belongs to: Science chemistry
Question #3
The extraction of aluminium is done by:
A. Reduction with carbon
B. Thermite process
C. Electrolysis of molten alumina in cryolite
D. Reduction with aluminium

Correct Answer: Option C


Explanation:
Aluminium is highly reactive; its oxide cannot be reduced by carbon. Hall-Héroult process electrolyzes alumina dissolved in molten cryolite (Na₃AlF₆) using carbon anodes.

This question belongs to: Science chemistry