What does this quote mean to you?
"You may need to fight a battle more then once to win."

Explanation:

I think it means that even if you dont succeed at something the first time you do it doesn't mean you sould give up.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements