Ionic and Covalent Bonding Section 4.2

What holds bonded atoms together? Atoms WANT their valence shells filled They bond with other atoms in such a way that these valence shells get filled up

More about bonds Bonds can stretch and bend without breaking There are 3 main types of bonds Ionic Bonds Metallic Bonds Covalent Bonds

Ionic Bonds Formed between oppositely charged ions Usually alkali metals & halogens Sometimes alkaline earth metals and halogens More rare combinations exist Form as networks, not individual molecules When melted or dissolved in water, they conduct electricity Formed by the transfer of electrons

Electron Transfer – Ionic Bonds + Fluorine FLUORIDE -

Ionic compounds form networks, not molecules

Metallic Bonds Form by the attraction between the nucleus of one atom and the electrons of its neighbors. - +

Electrons move freely between metal atoms in metallic bonds

Covalent Bond Facts Made of molecules, not network structures Often formed between nonmetal atoms Can be solids, liquids, or gases Most compounds of this type have low melting points Do not conduct electricity Atoms joined by covalent bonds SHARE electrons

Shared Electrons in Covalent Bonds

Atoms may share more than one pair of electrons

Polyatomic Ions Some compounds have BOTH ionic and covalent bonds. Example: Hydroxide (OH-) Hydrogen and oxygen covalently bonded Molecule is negatively charged, which behaves like an ion that can form an ionic bond

More Polyatomic Ions Carbonate Ammonium Cyanide