To determine the number of neutrons in an atom, we need to use the relationship between the mass number and the atomic number. Here are the steps:
1. Understand the terms:
- Atomic number: This is the number of protons in the nucleus of an atom. For aluminum (Al), the atomic number is 13.
- Mass number: This is the total number of protons and neutrons in the nucleus. For aluminum (Al), the mass number is 27.
2. Identify the given data:
- Atomic number ([tex]\( Z \)[/tex]) = 13
- Mass number ([tex]\( A \)[/tex]) = 27
3. Formula to calculate the number of neutrons:
The number of neutrons ([tex]\( N \)[/tex]) in an atom can be calculated using the following formula:
[tex]\[ N = A - Z \][/tex]
where:
- [tex]\( A \)[/tex] is the mass number (total number of protons + neutrons)
- [tex]\( Z \)[/tex] is the atomic number (number of protons)
4. Substitute the given values into the formula:
[tex]\[ N = 27 - 13 \][/tex]
5. Perform the subtraction:
[tex]\[ N = 14 \][/tex]
Thus, the atom of aluminum (Al) has 14 neutrons. Therefore, the correct answer is:
B. 14
