Question

A monatomic ion with a charge of -1 has an electronic configuration of 1s22s22p6. this ion is a(n) . what is the chemical symbol of the noble gas this ion is isoelectronic with? . what is the formula of the ion? .

Answer 1

1) this ion is an anion
cations are ions which have given out electrons and are positively charged 
anions are ions which have taken in electrons and are negatively charged. the ion given has a negative charge which means it has taken in an electron therefore its an anion.

2)what is the chemical symbol of the noble gas this ion is isoelectronic with ? atomic number of the ion is 10, this corresponds to the noble gas Neon - Ne.
chemical symbol is Ne

3) what is the formula of the ion?
the ion has a negative charge of -1. this means it has taken in one electron hence the electronic configuration before taking in the electron, when the atom is neutral is 1s² 2s² 2p⁵
then the atomic number is 9, element with atomic number is fluorine.
therefore element is F
formula of ion is F⁻