Answers

2014-10-02T20:08:05+08:00
First you have to learn octet rule: every atom needs to have 8 valence atom to become stable. and only the 'inert gasses' have complete 8 valence atoms. 

covalent means sharing of atoms. if you look at your table of elements, below every element has either + or - sign.+ means it is missing that many elctron and will attract elements with - to satisfy  the octet rule.example carbon has a 4 so he can bondwith 4 hydrogen who only has one.

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2014-10-02T21:42:31+08:00
Elements that usually form a covalent bond are the nitrogen group, chalcogens and halogens.
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