1. describe the difference between valence and core electrons.

The electrons present in outer most shell or higher energy level are valance electrons.

The electron present in inner most shell or lower energy level are called core electrons.

Explanation:

Valance and core electrons.

The electrons present in outer most shell or higher energy level are valance electrons, while the electron present in inner most shell or lower energy level are called core electrons.

The valance electrons take part in bonding while core electrons don't involve in bonding and influence the chemical reactivity of atoms.

The valance electrons form either a ionic bond or covalent bond during chemical reaction. These electrons involve in bond making and bond breaking process.

Example:

Consider the example of carbon. The atomic number of carbon is six.

Electronic configuration:

1s² 2s² 2p²

In this electronic configuration we can see that two electrons are present in 1s shell these are called core electrons. The electrons present in 2s and 2p are called valance electrons and take part in chemical reaction.