What thorium has 90 protons and 137 neutrons?

Answer : The representation of thorium isotope is

Explanation :

Isotope : It is defined as the element that have the same number of protons but have the different number of neutrons of each of the atom.

Atomic number is defined as the number of protons or number of electrons.

Atomic number = number of protons = number of electrons

Mass number is defined as the sum of number of protons and number of neutrons.

Number of neutrons = Mass number - Number of protons

Isotope notation : It is also called as nuclear notation. In isotopic notation we can easily determine an isotope's mass number, atomic number, the number of neutrons and protons in the nucleus.

The general isotopic representation of an atom is:

where,

Z = Atomic number of the atom

A = Mass number of the atom

X = Symbol of the atom

As we given:

Number of protons = 90

Number of neutrons = 137

Atomic number = number of protons = 90

Mass number = Number of neutrons + Number of protons

Mass number = 137 + 90

Mass number = 227

The symbol of thorium = Th

Thus, the representation of thorium isotope is