Carol has an unknown element in group 7. Using the periodic table, how many valence electrons does her element have? A.) Five
B.) Seven
C.) Nine
D.) Seventeen

seven

Explanation: the valence electrons are the numi of electrons found in the outermost shell of an element. The group of an element indicates it's number of electrons in the outermost shell while the number of shells occupied by electrons indicates the period.

Thus since the element is in group seven it has seven valence electrons.

oxygen = 21% of the atmosphere

nitrogen = 78%

carbon dioxide = 0.1%

argon =0.934%