Enter the appropriate symbol for an isotope of calcium-42 corresponding to the isotope notation AZX.

Express your answer as a chemical symbol using isotope notation.

40

20Ca

Answer is ₂₀⁴²Ca.

In AZX notation

A - Represents the mass number of atom.

Mass number = number of protons + number of neutrons.

It is shown at the above of the left side of the atom.

Here it is 42.

Z - Represents the atomic number.

Atomic number = number of protons.

It is shown at the bottom line of the left side of the atom.

Here it is 20.

X - Represents the symbol of the atom.

Here X is Ca.

The proton number number of the element stays constant in its isotopes while the mass number changes. So, for this isotope of Calcium:

42Ca20