₂₆⁵⁶Fe has 26 as the atomic number and 56 as mass number.
Mass number = number of protons + number of neutrons.
Since, atomic number = number of protons = 26,
number of neutrons = 56 - 26 = 30
Likewise,₂₆⁷³ Fe has 26 protons and 73 mass.
Hence the number of neutrons = 73 - 26 = 47
Hence, gained neutrons = 47 - 30 = 17
Hence, the equation should be,
₂₆⁵⁶Fe + 17n → ₂₆⁷³ Fe
