Question

The mass number of common krypton is 84, and its atomic number is 36. krypton-84 has how many neutrons within each isotope?

Answer 1

`"48 neutrons"`

Explanation:

The mass number, `A`, of a given isotope tells you the number of protons, `Z`, which is given by the atomic number, and neutrons it has in its nucleus.

`color(blue)(|bar(ul(color(white)(a/a)A = Z + "no. of neutrons"color(white)(a/a)|)))`

In your case, krypton-84 is said to have a mass number equal to

`A = 84`

This means that the nucleus of a krypton-84 isotope contains a total of `84` protons and neutrons.

Since the element has an atomic number equal to `36`, it follows that it will contain `36` protons in its nucleus. Therefore, the number of neutrons present in the nucleus of a krypton-84 isotope will be

`"no. of neutrons" = A - Z`

`"no. of neutrons" = 84 - 36 = color(green)(|bar(ul(color(white)(a/a)color(black)(48)color(white)(a/a)|)))`