Carbon has an atomic number of 6. how many electrons are in a carbon atom’s second energy level?

Carbon is an atom so electrons=protons 
First shell has 2 electrons and the next 8 so with 6 electrons the first shell fills and 4 are left to go into the 2th shell.

All the elements are arranged by melting points on the periodic table. in row they go from metals to gasses. in the row from sodium to argon, sodium is more reactive than the one on its right, magnesium.