A 2 - ion has 36 electrons and 45 neutrons. what is its correct symbol

Total electron element having = 36

In order to find number of Protons we will subtract 2 from 36 because 2 electrons are extra with respect to protons, So number of protons are,

# of protons = 36 - 2 = 34

Means, this element has atomic number 34 and electronic configuration of this element is,

1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁴

Now, Valence Shell = 4 = Element is present in Period 4

Valence Electrons = 6 = Element is present in Group 6

Result;

This element is Selenium, with atomic number 34 and atomic mass 79 (# of protons + # of neutrons). And the correct symbol is,

⁷⁹₃₄Se⁻²