Which indicates the energy that must be absorbed to initiate the reaction?

The activation energy.

Explanation:

Hello,

In chemical kinetics, the activation energy is defined as the required energy to allow a chemical reaction to be carried out. It is related with the energy content that will induce the atoms or molecules to crash, break the bonds or just become ionized and form the corresponding products based on the type of reaction. It could be represented graphically on the attached picture.

Best regards.

sodium (na), for example, has one electron in its valence shell. this is an unstable state because that valence shell needs eight electrons to be full. in order to fill its valence shell, find a way to add seven electrons to its valence shell

yes it is balanced