Chemical Bonds & Formulas+-+-

Chemical BondA force of attraction that holds two atoms togetherHas a significant effect on chemical and physical properties of compoundsinvolves the valence electronsValence Electrons the electrons in the outermost energy level of an atomThis Lithium Atom has onevalence electron

Carbon 4 valence electronsOxygen

6 valence electronsBeryllium

2 valence electronsCounting Valence Electrons

Oxidation NumberThe charge that an atom would have if it lost or gained electrons; ionic charge (an ion is a charged atom or molecule)Can be helpful in determining which atoms will interact or bond with each otherExample:According to electron dot diagram for Magnesium, it has two valence electrons. Because Magnesium is unhappy with two, it will typically lose them. If this happens it will turn into a Magnesium ion. At this point it will have an oxidation number of +2. Mg2+

IonsAnionis a charged atom or molecule. It is charged because the number of electrons do not equal the number of protons in the atom or molecule. An atom can have a positive or negative charge depending on whether the number of electrons in an atom is greater or less then the number of protons in the atom.

3 Types of Chemical BondsIonicCovalentMetallicWhat can you describe about each of thesebonds just by looking at the name?

Which different groups or familiesof elements will most-likelyinteract to create these typesof bonds?IONIC BONDS-The force of attraction between oppositely charged ions.Occurs after a transfer or loss/gain of electronsUsually form between atoms of metals and atoms of non-metalsResulting compounds have a name that usually ends in ideExample - Sodium Chloride (NaCl)ClNa1-1+

COVALENT BONDA force that bonds two atoms together by a sharing of electronsEach pair of shared electrons creates a bondUsually occurs between atoms of non-metals++Example Water (H2O)----------

Types of Covalent BondsDifferent covalent bond types share a different number of electronsSingle Bonds Share 2 ElectronsDouble Bonds Share 4 ElectronsTriple Bonds Share 6 ElectronsWater (H2O)Carbon Dioxide (CO2)Nitrogen (N2)

Unequal Sharing (Polar Covalent Bond)Why do you think the two Hydrogen atoms shareequally, but the Hydrogen and fluorine do not?+++Bonded hydrogen atoms showing equal sharing ofelectronsHydrogen and fluorine bond with an unequal sharing of electrons

The unequal sharing of electrons between two atoms that gives rise to negative and positive regions of electric charge Results from an atoms electronegativity the ability to attract electrons to itselfElectronCloud

Metallic BondA force of attraction between a positively charged metal ion and the electrons in a metalMany metal ions pass along many electronsMany properties of metals, such as conductivity, ductility, and malleability, result from the freely moving electrons in the metalUsually occurs between atoms of metals Notice how the electrons do not just stay with one ion--------------

Results of BondingMolecule A neutral group of two or more non-metal atoms held together by covalent bonds Type:

Diatomic - molecules consisting of two atoms of the same element bonded togetherExamples:H2, F2, O2, N2

Compound A pure substance composed of two or more different elements (atoms) that are chemically combined

Examples:CO, NO2, NaCl

What would you call something that has characteristics of both?

Chemical FormulasChemical formulas describe atoms held together by chemical bonds.Compounds are formed when elements share or transfer electronsCompounds with shared electrons are called covalent compoundsThe smallest unit of a covalent compound is called a moleculeExamples: H2O, NaCl, CO2 A chemical formula represents the smallest unit of a compound to show the elements in it.

Chemical EquationShorthand form for writing what reactants are used and what products are formed in a chemical reaction Sometimes shows whether energy is produced or absorbedExamples:

2H2 + O2 2H2O

CH4+2O2 CO2+2H2O

C6H12O6 + 6O2 6CO2 + 6H2O + energy

Components of a Chemical Equation 2H2 + O22H2O(Reactants)(Products)(Yield)Chemical FormulasChemical FormulaSubscriptsCoefficientSometimes you will see a yields sign that looks like this. What do you think it means?CoefficientSubscript

Energy and Chemical Reactions Exothermic Reaction A chemical reaction in which energy is released.The products have greater bond energy than the reactants

C6H12O6 + 6O2 6CO2 + 6H2O + energy(respiration)

Endothermic Reaction A chemical reaction in which energy is absorbed.The products have lower bond energies than the reactants

6CO2 + 6H2O + energy C6H12O6 + 6O2 (photosynthesis)Chemistry Comes Alive! Sample MoviesTeacherTube - VideosChemistry Demonstration Videos Can you think of other reactions where energy is gained or released?

Demo of EnergyHow can you tell if a reaction is endothermic or exothermic?

Rates of Chemical ReactionsTemperature a measure of the average kinetic energy of the particles in a sample of matter Ex. Increasing the temperature when cookingSurface area amount of material that comes into contact with the reactantsEx. Cutting a potato into smaller pieces when cookingConcentration amount of substance per volumeEx. Turning the valve on a gas stove to increase the concentration of methane molecules Catalysts (enzymes) organic substances that help speed up chemical reactions, but are not consumed in the reaction

The rates at which chemical reactions can take place arebased on the interaction (collisions) between the differentparticles. These rates can be impacted by the following:

VideoChemical Formulas: https://www.youtube.com/watch?v=KuNr4Rn17kk&list=PLJx6dVT-cbQW2NWa2uUiz3w15TlWwEV5e

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