#"1. the covalent bond;"# electron density is SHARED between atoms to allow close approach of the bound nuclei.
#"2. the ionic bond;"# electrons ARE TRANSFERRED between atoms (typically a metal and a non-metal) to form discrete charged particles that are held together by electrostatic attraction in an ionic lattice.
#"3. the metallic bond;"# the valence electrons of a metal centre are delocalized in a body of close-packed metal atoms. This gives rise to the familiar description of metallic bonding as #"positive ions in an electron sea"#. Metallic bonding gives rise to charactersitic metal properties: malleability; ductility; conductivity to heat and electricity.
Some compounds, i.e. compound ions, e.g. #Na_2CO_3#, #Na_2HPO_4# consist of ionic bonding between the charged particles, #Na^+, CO_3^(2-), HPO_4^(2-)#...BUT WITHIN the carbonate and biphosphate ions, the ATOMS are COVALENTLY bound.
