1. A chemical bond represents an attraction between atoms that allows for the formation of chemical substances that contain two or more atoms. The bond is caused by the electrostatic force of attraction that appears between opposite charges, either electrons and nuclei, or as the result of dipole attraction.
2. A covalent bond is formed between two non-metals that have similar electronegativities. Neither one of the two atoms are "strong" enough to attract electrons from the other, which means that they share these electrons.
An ionic bond is formed between a metal and a non-metal. Non-metals (or negative ions) are "stronger" than metals (or positive ions) and can take the electrons fairly easily from the metal; the ionic bond is formed because the two opposite ions attract each other.
3. In this case, the bond will be covalent, since we've already addressed the fact that atoms with similar electronegativities (in this case, equal electronegativities) will form covalent bonds.