Question

CO2 is a gas while SiO2 is a solid

Answer 1

I was under the impression that chemistry almost exclusively involves valence electrons because there isn't enough energy to strip off electrons located closer to the nucleus.

If that is true, and elements in the same period have similar properties because they have the same number of valence electrons, then why is

SiO
2
a solid and
CO
2
a gas

Answer 2

Co2 contains carbon and oxide which two elements react with each other and forms carbondioxide as well as Sio2 is the formation of silicon and oxide which reacts to form a solid , and having same valency and electrons doesnt mean to have same out comes coz all elements having same electrons are not same in nature they have different properties