Question

Which of the following atoms has the same number of neutrons as 9Be?

9B

10B

10Be

12C

Answer 1

Answer: -

¹⁰B has the same number of neutrons as ⁹Be

Explanation: -

Mass number of ⁹Be = 9

Atomic number of ⁹Be = 4

Number of neutrons of ⁹Be = mass number - atomic number

= 9 - 4 = 5

Mass number of ¹⁰B = 10

Atomic number of ¹⁰B= 5

Number of neutrons of ¹⁰B= mass number - atomic number

=10 - 5 = 5

Answer 2

Answer : Option B) $^{10}B$

Explanation : The option which has same number of neutrons as that of $^{9}Be$ is $^{10}B$

As, $^{10}B$ has 5 neutrons in its atom, the mass number of $^{10}B$ is 10.

So, when it has 5 protons and 5 electrons in it then it would has 5 neutrons which is similar to that of $^{9}Be$.

$^{9}Be$ has 4 protons and 4 electrons in its atom which means it has (9 - 4) = 5 neutrons.

From, the above it is clear that $^{10}B$ is the correct choice amongst the given options.