Question

which of the following statements about valence electrons and the periodic table is true

Answer 1

The electrons in the outermost shell are the valence electrons--the electrons on an atom that can be gained or lost in a chemical reaction. Since filled d or f subshells are seldom disturbed in a chemical reaction, we can define valence electrons as follows: The electrons on an atom that are not present in the previous rare gas, ignoring filled d or f subshells.

Gallium has the following electron configuration.

Ga: [Ar] 4s2 3d10 4p1

The 4s and 4p electrons can be lost in a chemical reaction, but not the electrons in the filled 3d subshell. Gallium therefore has three valence electrons.