its c with the older down the older it is
Explanation:
When an atom has an equal number of electrons and protons, it has an equal number of negative electric charges (the electrons) and positive electric charges (the protons). The total electric charge of the atom is therefore zero and the atom is said to be neutral. ... Chemically, we say that the atoms have formed bonds.
The group is might be labeled as VIIB or VIIA.
I'm in the car now so can't lookup periodic table. But you find molecular weight of: 1 Ca + 2 Cl
Then that
Distance and time is needed for determining speed