Question

Many elements have fractional atomic mass. This is because of :

• A. they have isotopes
• B. their isotopes have non-integral masses
• C. their isotopes have different masses
• D. neutrons, protons and electrons combine to give fractional masses

Answer 1

Answer: (A), (C)

they have isotopes
their isotopes have different masses

Several elements have isotopes with different atomic masses. Hence, many elements have fractional atomic masses.

Thus, options A and C are correct.

For example, chlorine has two isotopes with atomic masses $35$ and $37$ with a natural abundance ratio of $3:1$.

$\frac{35\times 3+37\times 1}{4}=35.5$

The weighted average atomic mass is $35.5$.