Ionic/Covalent/Metallic Bonding Notes

Stable or Unstable? An atom is only stable if it has a full valence shell If an atom is stable, it will not bond If an atom is not full, it will bond

Compounds Compounds are formed when 2 atoms of different elements bond together. Atoms bond to fill their valence shell An atom will bond with an many atoms as it takes to fill its outer shell Once the valence shell is full, that atom is stable

ION – any atom with more or less electrons than it is supposed to have* *Remember that the number of electrons is supposed to be equal to the number of Protons if the atom has a neutral charge

Types of Chemical Bonds There are 3 types of chemical bonds: Ionic Bonds Covalent Bonds Metallic Bonds

Ionic Bonds Ionic bonds exist between a metal and a nonmetal When two atoms bond ionically, they gain/lose electrons. Electrons are transferred from one atom to another. When an atom gains or loses an electron, it becomes an ion

Ions Ca +2 +2 +2 +2 +2 +2 +2 It has 2 valence electrons. How many does it need to be stable? 8…so it can either lose 2 or gain 6. Which is easier? Calcium is in group 2. How many valence electrons does it have? Which other elements would lose 2 electrons? Group 1 18 2 13 14 15 16 17 3 4 5 6 7 8 9 10 11 12 Losing 2…if it loses 2 electrons, it becomes positive Ca +2 +2 +2 +2 +2 +2 +2

Ions +1 +1 +2 +3 +4 -3 -2 -1 +1 -2 +2 +3 +4 -3 -1 +1 -2 +2 +3 +4 -3 -1 Group 1 18 2 13 14 15 16 17 3 4 5 6 7 8 9 10 11 12 +1 +1 +2 +3 +4 -3 -2 -1 +1 -2 +2 +3 +4 -3 -1 +1 -2 +2 +3 +4 -3 -1 +1 +2 +3 +4 -3 -2 -1 +1 +2 +4 -3 -2 -1 +3 +1 +2

Ionic Bonds Properties of Ionic Compounds High melting point Good conductor of electricity Solid at room temperature

Covalent Bonds Covalent bonds exist between NONMETAL and NONMETAL. Example: H2, H2O, NO3, CH4 Covalent bonds SHARE electrons. Shared electrons don’t belong to either atom.

Covalent Bonds Properties of Covalent Compounds Low melting point Poor conductor of electricity Liquid or Gas at room temperature

METALLIC BOND bond found in metals; holds metal atoms together very strongly

Metallic Bond Formed between atoms of metallic elements Electron cloud around atoms Good conductors at all states, lustrous, very high melting points Examples; Na, Fe, Al, Au, Co

Lewis Structures of molecules Single Bond: Two atoms sharing one electron pair. Example: H2 Double Bond: Two atoms sharing two pairs of electrons. Example: O2 Triple Bond: Two atoms sharing three pairs of electrons. Example: N2 Resonance Structures: More than one Lewis Structure can be drawn for a molecule. Example: O3

Rules for Drawing Lewis Structures Carbon dioxide, CO2 Total Number of valence electrons = 4 + (2 x 6) = 16 Double bonds Rules for Drawing Lewis Structures First sum the number of valence electrons from each atom The central atom is usually written first in the formula Complete the octets of atoms bonded to the central atom (remember that H can only have two electrons) Place any left over electrons on the central atom, even if doing so it results in more than an octet If there are not enough electrons to give the central atom an octet , try multiple bonds E.x. 1. PCl3 Total Number of valence electrons = 5 + (3 x 7) = 26

1. Odd Number of Electrons NO Number of valence electrons = 11 Resonance occurs when more than one valid Lewis structure can be written for a particular molecule (i.e. rearrange electrons) NO2 Number of valence electrons = 17 Molecules and atoms which are neutral (contain no formal charge) and with an unpaired electron are called Radicals O2