Question

How many neutrons does Fe have?

Answer 1

The number of neutrons present in the nucleus is calculated by subtracting the mass number of the atom with the atomic number of the atom. The mass number of the atom is the sum of the number of protons and neutrons.

Complete step by step answer:
The atom is the smallest unit which forms a chemical element. Each atom is formed of a nucleus or one or more than one electrons surrounding the nucleus. The nucleus is formed of one or more protons and the number of neutrons.
The number of protons in the nucleus of the atom is equal to the atomic number (Z). The number of electrons in a neutral atom is equal to the number of protons. The mass number of the atom is defined as the sum of the number of protons and neutrons present in the nucleus.
The number of neutrons present in the nucleus is equal to the difference between the mass number of atom (M) and the atomic number (Z).
$Number\;of\;neutron = mass\;number - atomic\;number$
The iron is the chemical element with symbol Fe. The atomic number (Z) of Fe is 26. The mass number of iron Fe is 55.845.
The number of neutrons of iron Fe is calculated as shown below.
$\Rightarrow Number\;of\;neutrons = 55.845 - 26$
$\Rightarrow Number\;of\;neutrons = 29.845 \approx 30$
Therefore, the number of neutrons in iron (Fe) is 30.

Note:
The mass number is also known as atomic mass and its unit is atomic mass unit. The isotopes of Fe are ${}^{54}Fe$, ${}^{56}Fe$, ${}^{57}Fe$ and ${}^{58}Fe$, where the mass number is different for each isotope but the atomic number is same. So, the number of neutrons for each isotope of iron (Fe) will be different.