3Electron ShellsAtomic number = number of ElectronsElectrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells.Electron shells determine how an atom behaves when it encounters other atoms
4Electrons are placed in shells according to rules: The 1st shell can hold up to two electrons.Each shell thereafter can hold up to 8 electrons.
5H would like toC would like toN would like toO would like toGain 1 electronGain 4 electronsGain 3 electronsGain 2 electrons
6IONIC BOND A bond formed between two elements by the transfer of electrons
7Formation of Ions from Metals Ionic compounds result when metals react with nonmetalsMetals lose electrons to gain a full outer electron shell (the next electron shell becomes the new outer shell)Positive ions form when electrons are lostGroup 1A metals ion +1Group 2A metals ion +2Group 3A metals ion +3
8Formation of Ions from Nonmetals Nonmetals gain electrons to gain a full outer electron shellNegative ions form when electrons are gainedGroup 5A nonmetals ion -3Group 6A nonmetals ion -2Group 7A nonmetals ion -1Group 8A elements do not gain or lose electrons since they already have a full outer shell.
111). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.
12Properties of Ionic Compounds Individual atoms are bound tightly together forming crystal structuresHigh melting pointsHigh boiling pointsConduct electricity when melted or in solutionMany can be dissolved in water
14COVALENT BOND A bond formed between two elements by the sharing of electrons.
15How to Draw Covalent Bonds 1. Draw dot diagrams for each elementFigure out how many electrons need to be SHAREDShow sharing of electrons by connecting the dots.Ex: Hydrogen and Oxygen.H needs 2 valence e to be stable, O needs 8 total but only has 6.They need to share electrons because they are both non-metals.
18when electrons are shared equally NONPOLAR COVALENT BONDSwhen electrons are shared equallyH2 or Cl2
19Covalent bonds- Two atoms share one or more pairs of outer-shell electrons. Oxygen AtomOxygen AtomOxygen Molecule (O2)
20when electrons are shared but shared unequally POLARCOVALENT BONDSwhen electrons are shared but shared unequallyH2O
21Polar Covalent Bonds: Unevenly matched, but willing to share.
22Water is a polar molecule because oxygen has a stronger charge than hydrogen, and therefore electrons are pulled closer to oxygen.
23Properties of Covalent Compounds Form irregular structures (no set geometric shapes like crystals)Low melting and boiling pointsPoor conductors of electricity in all phasesMany do not dissolve in water
24METALLIC BOND Bond found in metals which holds metal atoms together very strongly
25Metallic BondFormed between atoms of metallic elementsElectron cloud around atomsGood conductors at all states, hard, very high melting pointsExamples; Na, Fe, Al, Au, Co