What is the compound formed when potassium reacts with chlorine?

Answer 1

The compound formed is KCl.

K is in group 1 on the Periodic Table, it wants to lose 1 electron to be like the nearest noble gas (i.e. fulfill the octet rule - look at the Periodic Table to see what the closest noble gas is to the element in question, i.e. He, Ne, Ar, etc. In this case, K wants to lose 1 electron to be like Ar).

Cl is in group 7 on the Periodic Table, it wants to gain 1 electron to be like the nearest noble gas (i.e. fulfill the octet rule).

So,

K is -1

Cl is +1

Put them together and they are perfectly happy (i.e. have fulfilled the octet rule).

Another example, B reacting with Cl;

B = group 3 = wants to lose 3 electrons to be like the nearest noble gas.

Cl = group 7 = wants to gain 1 electron to be like the nearest noble gas.

B is -3

Cl is +1

Therefore, BCl3 is the answer.