Question

which type of compound is made up ofatoms held together by convalants bonds

Answer 1

molecular compounds are made up of covalent bonds because they "share" electrons

Answer 2

how are atoms in molecules held together

Answer 3

Through the sharing of electrons

Answer 4

@bmelyk all compounds are molecular, because they're made up of molecules :P

covalent bonds are subdivided into:
non-polar = atoms have equal sharing of electrons

polar = atoms share electrons unequally, the more electronegative atom in the molecule has greater affinity for the electrons, the electrons "spend more time" near this atom and induce a partial negative charge. Conversely, the less electronegative atom has a partial positive charge due to this unequal sharing.
Polar molecules have a dipole moment (which a vector-a magnitude with direction) which can be measured from the difference in electronegativity between the atoms. Pauling's scale is most common and found on most periodic tables.