To determine the number of neutrons in an atom, you use the relationship between the mass number, the number of protons, and the number of neutrons.
1. Understand the given information:
- The atom of beryllium has 4 protons.
- The mass number of the atom is 9.
2. Recall the formula:
- The mass number is the sum of the protons and neutrons in the nucleus of an atom. This can be expressed as:
[tex]\[ \text{Mass Number} = \text{Number of Protons} + \text{Number of Neutrons} \][/tex]
3. Set up the equation:
[tex]\[ 9 = 4 + \text{Number of Neutrons} \][/tex]
4. Solve for the number of neutrons:
- Subtract the number of protons from the mass number to find the number of neutrons:
[tex]\[ \text{Number of Neutrons} = 9 - 4 \][/tex]
[tex]\[ \text{Number of Neutrons} = 5 \][/tex]
5. Thus, the atom of beryllium contains:
- 5 neutrons.
The correct answer is:
05
