Question

The atomic number and mass number of an isotope of chlorine are 17 and 37. Calculate the number of neutrons and protons in the nucleus of the atom

Answer 1

Number of protons = number of electrons = 17

Number of neutrons = mass number - atomic number = 37 - 17 = 20

The atom is chlorine.

Answer 2

Neutral atoms of each element contain an equal number of protons and electrons.

The number of protons determines an element’s atomic number and is used to distinguish one element from another.

The number of neutrons is variable, resulting in isotopes, which are different forms of the same atom that vary only in the number of neutrons they possess.

Together, the number of protons and the number of neutrons determine an element’s mass number.

Since an element’s isotopes have slightly different mass numbers, the atomic mass is calculated by obtaining the mean of the mass numbers for its isotopes.