MCQ practice · SSC Chemistry Board questions · Chapter 3: Structure of Matter
What is the actual mass of an electron?
Think it through first, then pick an option.
- a 1.673 × 10⁻²⁴ g
- b 1.675 × 10⁻²⁴ g
- c 9.11 × 10⁻²⁸ g
- d 9.11 × 10⁻³¹ g
Answer and explanation
Correct answer: c 9.11 × 10⁻²⁸ g
In grams, the electron's mass is 9.11 × 10⁻²⁸ g.
Why the other options are wrong
- a 1.673 × 10⁻²⁴ g: This is the proton's mass; the electron's is 9.11 × 10⁻²⁸ g.
- b 1.675 × 10⁻²⁴ g: This is the neutron's mass; the electron's is 9.11 × 10⁻²⁸ g.
- d 9.11 × 10⁻³¹ g: The number is right but the unit is wrong: 9.11 × 10⁻³¹ is in kilograms; in grams it is 9.11 × 10⁻²⁸ g.
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