neutrons and protons are inside the neclues of the atom protons are positively charged while electrons are negatively charged while neutrons are neutral, only electrons can be lost or gained when a reaction occurs, so if an atom was to lose an electron it would be positively charged as there is an unequal balance of positive and negative charges, and if it was to gain an electron it would be negatively charged, covalent bonding is when a molecule has a shaired pair of electrons covalent bonding usually happens with non-metal atoms only for hydrogen bonds check this http://en.wikipedia.org/wiki/Hydrogen_bond
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Kyle