What is electron configuration and valence electrons?

Answer 1

Mostly they are s or p electron sub-orbitals in the same (outer) shell.

In the transition metals sometimes one electron from a higher d orbital gets involved ( e.g. to reach the oxidation states Fe2+ and Fe3+).

Answer 2

The electron configuration of an atom is a numerical representation of the number of electrons in an atom. The numerical representation is divided into levels and sub levels identified by the period and group in which the atom is in

Period ----- Shell ----- Atom pairs

1 ------------- s ------------- 1

2 ----------- s, p -----------1, 3

3 ----------- s, p -----------1, 3

4 --------- s, p, d -------- 1, 3, 5

5 --------- s, p, d -------- 1, 3, 5

Each pair represent 2 atoms. The s shell can hold 2 electrons, the p shell can hold 6 electrons, and the d shell can hold 10 electrons

The valence of an atom is also identified by the shell and sublevel it is in. All the valence of an electron tell you is how many electrons exist in it's outermost shell

Answer 3

Electron configuration is the arrangement of electrons in an atom's orbitals. It is often represented using a notation that indicates the energy levels and sublevels where the electrons are located.

Valence electrons are the electrons in the outermost energy level of an atom. They are involved in chemical bonding and determine the reactivity of an element.