The number of neutrons in an atom of ¹³¹I is A - VCE - SSCE Chemistry - Question 1 - 2004 - Paper 1

To find the number of neutrons in an atom, you can use the formula:

$\text{Number of Neutrons} = \text{Mass Number} - \text{Atomic Number}$

In this case, the mass number of iodine-131 (¹³¹I) is 131. The atomic number (which represents the number of protons) of iodine is 53. Therefore:

$\text{Number of Neutrons} = 131 - 53 = 78$

Thus, the number of neutrons in an atom of ¹³¹I is 78.