80Hg198 and 79Au197 can be termed as which of the following?

The correct answer is Option 2: Isotones

Nuclides with same neutron number but different atomic number are called Isotones.

Both ₈₀Hg¹⁹⁸ and ₇₉Au^{197 have the same number of neutrons, so they are isotones.}

Number of neutrons = Mass number − Atomic number
For Hg: 198−80=118
For Au: 197−79=118