Which of the following tend to possess the same number of outer electrons? A. all molecules with the same number of atoms B. all elements within the same group C. all molecules made up of the same elements D. all elements within the same period

the answer would be "B"

Explanation:

Elements with the same number of valence electrons are found in the same column of the Periodic Table. All elements in the first column of the Periodic Table have 1 valence electron in an s orbital. These elements are known as Group 1A metals or alkali metals.

c (diamond),

sio2 (quartz)