Potassium is the major cation in the body. It plays many important roles, including the excitability of nerves and muscles. Where is this action particularly important

in the heart

Explanation:

hope it's help

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds