# Does an atom want to give or take electrons when it has a shell half full?

For example, carbon has 4 electrons in the outer shell and so its half full. Does it want to give electrons in a bond or take electrons, and if any atom has a half full electron shell does it want to take or give electrons for a covalent bond? I'm new to chemistry so this question may be simple.

## 1 Answer

When it comes to elements like carbon and silicon, which have 4 valence shells, the maximum possibility is sharing of electrons to form covalent bonds, like in $\ce{CO2}$ or $\ce{CH4}$. However in carbides, like calcium carbide or tungsten carbide, it may gain electrons.

• Thanks also If an atom like Boron has only 3 electrons in the outer shells, will it give up its electrons for a bond? and vice versa for nitrogen where it would take electrons for a bond? – Physix Jan 23 '16 at 16:24
• Atoms with 1,2,3 electrons lose electrons to form cations(positively charged) while atoms with 5,6,7 electrons gain electrons to form anions(negatively charged) (or share as discussed) So boron will give 3 electrons and Nitrogen will accept electrons...So yeah u're right – Krutika Zambre Jan 23 '16 at 16:27
• Except when they don't. There are a whole range of cations with positive charges on nitrogen whereas boron cations are quite rare. Much more common are electron deficient covalent boron compounds. – bon Jan 23 '16 at 16:29
• Boron cations are rare due to much less electropositivity( refer to periodic trends in the 2nd period of the periodic table) And when it comes to positive charge, are you referring to ionization due to polarity? – Krutika Zambre Jan 23 '16 at 16:33