5 Chemical BondingCompounds are formed from chemically bound atoms or ions.Bonding involves only the valence electrons.When atoms combine we call them molecules.
6 Valence ElectronsElectrons are found in specific orbits/clouds spinning around the nucleusValence electrons are the electrons located in the outermost orbitElements become stable when:their outer orbit contains 8 electrons or their outer orbit becomes emptyLewis Dot Diagrams show the # of Valence Electrons
8 The Octet RuleWhen the highest energy level of an atom is filled, the atom is stable.Atoms tend to gain, lose, or share electrons until they have eight valence electrons.Hydrogen and Helium are the only exceptions. Because they are so small, they are satisfied with two valence electrons.Why are the noble gases unreactive?
10 Lewis Symbols / Electron Dot Diagram Lewis symbols show the valence electrons as dots arranged around the atomic symbol.hydrogen:sodium:chlorine:HNaCl· ·
11 Lewis Dot Diagrams of Selected Elements Show the number of valence electronsLewis Dot Diagrams of Selected Elements
12 Oxidation #An oxidation number indicates how many electrons are lost or gained during the bonding process.Mg loses 2 electrons so it has an oxidation number of +2Oxygen gains 2 electronsso it has an oxidationnumber of –2.
13 The periodic table show the common oxidation numbers for groups on the periodic table.
14 = Ionic Bonds – formed when atoms gain or lose electrons. Ex: Na has 1 valence e-=
15 When Na loses that electron, its 2nd E.L. becomes full andstable with 8 e-.Atoms with an electricalcharge are called ions.
16 IonizationWhen an atom loses or gains electrons they become ions – or atoms with an electrical charge.If an atom LOSES an electron, it becomes an ion with a +1 charge.If an atom GAINS an electron, it becomes an ion with a –1 charge.
17 Chlorine has 7 valence electrons. If Cl gains 1 electron, its valence shell will be full and stable.
20 Ionic Bonds Na Cl Cation Anion form between a metal and a nonmetal form as a result of a transfer of electronsNa becomes a positive ion =Cl becomes a negative ion =Cation means “to go down”– also think cast offAnion means “to go up”Also think acceptNaCl· ·CationAnion
21 Ions 1. Positively or negatively charged atoms. 2 Ions Positively or negatively charged atoms (Number of protons not equal to thenumber of electrons.) 3. Metals – give up electrons to form positive ions.(example: ) 4. Nonmetals – take in electrons to formnegative ions. (example: )
22 Ionic BondsWhat is the formula for the compound that forms between magnesium and chlorine?Cl· ·Mg· ·Cl· ·
24 Ionic CompoundsIonic compounds consist of a lattice of positive and negative ions.
25 Ionic Compounds, Characteristic Properties High melting pointsHigh boiling pointsConduct electric current when melted and when dissolved in solutionAll of these properties are a result of the strong attraction among ions within the crystal lattice
26 Animated Reaction sodium and chlorine Youtube video of sodium reacting with chlorine
27 Covalent Bonds form between two nonmetal atoms form as a result of a sharing of electrons
28 Covalent Bonding Most atoms share electrons to gain an octet. Covalent bonds are formed when e- are shared.
30 Diatomic molecules: – covalently bonded atoms of the same type. Exs: H Cl F2I O Br N2
31 Polar MoleculesThe type of atoms and their shape determine if a molecule is polar or notWith polar molecules there is an uneven distribution of charge…one atom has a stronger attraction for the electrons than the otherPolar molecules attractions are stronger than nonpolar molecules
33 Molecular Compounds, Characteristic Properties Note the correct name for a compound that contains covalent bondsLow melting pointsLow boiling pointsUsually gases or liquids at room temp.Does not conduct electricity wellMay or may not dissolve in water (there are several types of molecular compounds)
34 In GENERAL:Ionic Bonds–metal / nonmetalCovalent Bonds–2 nonmetals
35 Double Bubble – Compare/Contrast Ionic and Covalent Bonding
36 Double Bubble – Compare/Contrast Ionic and Covalent Bonding