Answer:
7 Valence Electrons.
Step-by-step explanation:
The Valence electrons are referred to as the number of electrons in the outermost shell of an atom.
When given the electronic configuration, the valence can be calculated by adding the superscript of the hugest number coefficient.
The highest number coefficient in this electronc cnfiguration is 2. The sum of it's superscript is 2 (in 2s²) and 5 ( in 2p⁵). That is 2 + 5 = 7
How to test the answer?
The atom given has 9 electrons ( 2 + 2 + 5).
The K shell is being occupied by 2 electrons, the next shell; M shell which can occupy maximum of 8 electrons is being occupied by 7 electrons ( 9 - 7). And in this atom, the M shell is the outermost shell.