Answer :
To determine the number of protons and neutrons in an atom, we need to use the information given by its atomic number [tex]\( Z \)[/tex] and mass number [tex]\( A \)[/tex].
1. Atomic Number ([tex]\( Z \)[/tex]):
- The atomic number represents the number of protons in the nucleus of the atom.
- For this atom, [tex]\( Z = 31 \)[/tex]. Thus, the atom has 31 protons.
2. Mass Number ([tex]\( A \)[/tex]):
- The mass number represents the total number of protons and neutrons in the nucleus of the atom.
- For this atom, [tex]\( A = 69 \)[/tex]. This number is the sum of protons and neutrons.
3. Neutrons Calculation:
- To find the number of neutrons, we subtract the atomic number from the mass number:
[tex]\[
\text{Number of neutrons} = A - Z
\][/tex]
- Substituting the given values:
[tex]\[
\text{Number of neutrons} = 69 - 31 = 38
\][/tex]
Therefore, the atom contains 31 protons and 38 neutrons.
So, the correct answer is:
```
31; 38
```
1. Atomic Number ([tex]\( Z \)[/tex]):
- The atomic number represents the number of protons in the nucleus of the atom.
- For this atom, [tex]\( Z = 31 \)[/tex]. Thus, the atom has 31 protons.
2. Mass Number ([tex]\( A \)[/tex]):
- The mass number represents the total number of protons and neutrons in the nucleus of the atom.
- For this atom, [tex]\( A = 69 \)[/tex]. This number is the sum of protons and neutrons.
3. Neutrons Calculation:
- To find the number of neutrons, we subtract the atomic number from the mass number:
[tex]\[
\text{Number of neutrons} = A - Z
\][/tex]
- Substituting the given values:
[tex]\[
\text{Number of neutrons} = 69 - 31 = 38
\][/tex]
Therefore, the atom contains 31 protons and 38 neutrons.
So, the correct answer is:
```
31; 38
```
