How many valence electrons are represented in the following electron configuration? 1s22s22p5 a)2 b)4 c)5 d)7

Answer is: d) 7.
Electron configuration: 1s²2s²2p⁵.
Valence electrons are in 2s and 2p orbitals.
Valence electrons are outer shell electrons (transition metal can have a valence electrons in an inner shell) that is associated with an atom and they can form chemical bond. Valence eletrons determine chemical proporties of element.