Question

How many protons and how many neutrons are in$\text{(a)}{}^6\mathrm{Li},\text{(b)}{}^{54}\mathrm{Cr}\text{, (c)}{}^{54}\mathrm{Fe}\text{, and (d)}{}^{220}\mathrm{Rn}\text{?}$

Short answer

Therefore,

a.) 3

b.) 30

c.) 28

d.) 134

Step-by-step solution

Given information

$\text{(a)}{}^6\mathrm{Li},\text{(b)}{}^{54}\mathrm{Cr}\text{, (c)}{}^{54}\mathrm{Fe}\text{, and (d)}{}^{220}\mathrm{Rn}\text{?}$

Explanation (a)

The nucleus is made up of Z protons and A - Z neutrons, as we know.

a.) We have ⁶Li

Atomic number is: 3

Number of protons is: 3

So, number of neutrons for ⁶Li is: 6-3 = 3

Explanation (b)

b.) We have ⁵⁴Cr:

Atomic number is: 24

Number of protons is: 24

So, number of neutrons for ⁵⁴Cr is 54-24 = 30

Explanation (c)

c.) We have ⁵⁴Fe

Atomic number is: 26

Number of protons is: 26

So, number of neutrons for ⁵⁴Fe is 54-26 = 28

Explanation (d)

d.) We have ²²⁰Rn

Atomic number is: 86

Number of protons is: 86

So, number of neutrons for ²²⁰Rn is 220- 86 = 134