Answer: The number to the left of AC should be 6.
Explanation: The balanced chemical reaction is one in which the number of atoms of each element on the reactant side must be equal to the number of atoms on product side.
The given equation
is unbalanced as the atoms on the reactant side are not same as number of atoms on product side. This equation is called as skeletal equation.
The balanced chemical equation is :

Thus the number to the left of AC is 6.
Argon is a noble gas. Argon has a full outer shell. This makes it so that it does not need to react with any of the other elements to be stable.
With Rubidium and Cobalt its a whole different story.
I hope that helps!
Answer:- There are 32 valence electrons and it's tetrahedral in shape.
Explanations:- Atomic number of carbon is 6 and it's electron configuration is
. It has 4 electrons in the outer most shell means it has 4 valence electrons.
Atomic number of Br is 35 and it's electron configuration is
. It has 7 electrons in the outer most shell(2 in 4s and 5 in 4p) .
There is one C and four Br in the given compound. So, total number of valence electrons = 4+4(7) = 4+28 = 32
Four Br atoms are bonded to the central carbon atom and also there isn't any lone pair present on carbon. It makes it tetrahedral.
Sorry i cant even read that