In which group does each element have a total of four electrons in the outermost principal energy level

Group 14  

Explanation:

The elements of the Periodic Table are arranged into 18 Groups.

Among the "main group elements" — those in Groups 1, 2 and 13 to 18 — the number of valence electrons —  the number of electrons in the outermost energy level —  corresponds to the last digit of  the Group number.

Thus, Group 14 contains the elements with four valence electrons — C, Si, Ge, Sn, Pb, and Fl.

14 days is the half-life of phosphorus-32

a electronegativity decreases beacuse the size of nucleus is bigger.