Chapter 6 Section 1 Compounds and Molecules Structure of Matter Chapter 6 Section 1 Compounds and Molecules

Chemical bonding A joining of atoms to form new substances (molecules) This is a chemical change, the new substances will have different properties than the original elements. Chemical bonding involves valence electrons

Why atoms bond? Atoms are most stable (happy) with a full valence shell. A full valence is normally 8 e- (for H, He, Li and Be it is 2) Bonding is an atoms sharing or transferring electrons trying to get to a full valence shell.

Types of bonds Ionic bonding- a transfer of electrons (something gains, something loses) Metal + Nonmetal Covalent bonding- a sharing of electrons 2 Nonmetals Metallic bonding- electrons being shared and transferred throughout a compound 2 Metals

Chemical Structure Water’s chemical formula tells us what atoms make up water, but it doesn’t tell us anything about how it is put together or how it acts. Chemical Structure: how the atoms are bonded together to make the compound

Bond Length and Angle Bond length: the distance between nuclei of two bonded atoms Bond Angle: the angle formed by two bonds to the same atom, tells which way these atoms point.

Why Bond? Atoms join to form bonds so that each atoms has a stable electron configuration. http://www.youtube.com/watch?v=66kuhJkQCVM Bill Nye on chemical reactions

What are ionic bonds? Ionic bonding- a transfer of electrons Ionic bonds occur between metals and nonmetals

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Chemical Compounds Chapter 6 section 2

Ionic and Covalent Compounds An element is something that can not be broken down any further. It is made up entirely of the same atom. Compounds are pure substances composed of the same ions and/or molecules. Compounds can be broken down into other substances.

Ionic and Covalent Compounds Ionic bonds are a transfer of electrons. Covalent bonds are a sharing of electrons. In an ionic bond, an electron leaves one atom and goes to another. In a covalent bond, the electron travels around two atoms.

What holds them together? bond implies they are stuck together, but there is nothing shared between them. Ionic bonds are held together by electromagnetic force (opposites attract) so Na+ is attracted to Cl- when large amounts get together they stack in a crystal arrangement

Crystal Arrangement There isn’t exactly an ionic “molecule”, just a ratio of loose ions stacked together. They Make a network. This is sometimes called a formula unit.

Dissolving Ions If you dissolve ions in water, they will break apart into parts. Some will have a positive charge, some will have a negative charge. Because of this difference in charge IONIC COMPOUNDS conduct electricity.

Ionic Compounds Compounds that contain ionic bonds are ionic compounds. Salts, baking soda, and rust are examples of ionic compounds. Ionic bonds are a force of attraction between oppositely charged ions. Ions are charged particles and are formed when they gain (nonmetals) or lose (metals) electrons.

Ionic Compounds Properties Brittle- Ionic compounds tend to shatter when hit High Melting points- most ionic bonds don’t melt until they are very hot Solubility- many ionic compounds tend to dissolve in water. Water is a polar solvent and ionic compounds have positive and negative ends, which the water pulls on.

Covalent Bonding A sharing of electrons The electrons are traveling somewhere in that blue bubble

Covalent Compounds Covalent compounds can be solids, liquids or gases They don’t usually conduct electricity because they don’t have an overall charge

Covalent Compounds Covalent Compounds are made of molecules. Molecules are atoms that share electrons in a bond. Glass, rubbing alcohol, nitroglycerin, and natural gas are all covalent compounds.

Covalent Compounds Properties Low melting points- several compounds exist as gases or liquids at room temperature. Most covalent compounds do not dissolve in water or produce positive and negative particles if they do dissolve. Therefore most covalent compounds do not conduct electricity by themselves.

Polarity Some atoms don’t share electrons equally Sometimes the electron is more attracted to one side than the other causing the compound to be POLAR If the electrons are shared equally they are said to be NONPOLAR COVALENT BONDS

Water and Conductivity Pure water (highly polar) does not conduct electricity. In order to conduct electricity, water must have positive and negative particles in it. Dissolving ionic compounds puts positive and negative particles in the water increasing the conductivity of water. Electrolyte- anything dissolved in water that increasing the conductivity GATORADE

Metallic Bonding Bonds between metals Both a sharing and a transfer of electrons Metallic bonds only occur with the same metal not with other metals Ca can bond with other Ca atoms, but not Ba

Metallic Bond In metallic bonds the valence electrons become community property, traveling anywhere they want to throughout the element. This “Sea of Electrons” is why metals are such good conductors of electricity and heat.

Model of Metallic Bonds Calcium has 2 valence electrons Ca Ca All of them move like this. Ca Ca Ca Ca The “sea of electrons” is kind of like bees (valence electrons) swarming around a few hives (rest of the atom)

Metallic Bonds Metallic Bonding is when all valence electrons are free to move from atom to atom. A metallic bond only occurs between two of the same metal atom. Copper can form a metallic bond with another copper atom but not with a gold atom. Metals are flexible and can conduct electricity.

Polyatomic ions Some compounds have both covalent bonds and ionic bonds

Compound Names and Formulas Chapter 6.3

Naming ionic compounds For anions: anions gain electrons For nonmetals only (the right side of the periodic table) drop the ending and add “-ide” so F- fluoride Cl-, O2-, C4- chloride, oxide and carbide

Cations: An Ion that has a positive charge because it gave an electron to another element Examples: Litium ion Potassium ion Calcium ion

Continuing… Metals keep the name of the element. When naming compounds always name the metal (cation) first and the nonmetal (anion) last. so mixing ions of chlorine and sodium give you sodium chloride (metal) (nonmetal)

Determining the formula of ions Ionic compounds are neutral (remember, they want to be happy so being neutral is most stable) You need to find the lowest number of each ion to make it neutral for example: Na+ and O2- 2 sodium for every one oxygen Na2O

Determining Charge (how do you do this?) Remember everything in group 1 is +1 Everything in group 2 is + 2 Aluminum is + 3 Halogens (group 17) are -1 Oxygen group is -2 Nitrogen group is -3

Remember: The number of valence electrons are the ones that want to react…… If you have fewer electrons you are likely to give up your electrons to something else (and then you become more positive) If you have more electrons (but not 8, you will accept electrons easier, so become more negative)

More examples Al3+ and O2- K+ and Cl- Al2O3 K+ and Cl- KCl the subscripts don’t effect the name if there is only one possibility still (cation)(anion) Aluminum oxide Potassium chloride

Several metals can form a couple of different ions. These are all metals that aren’t in group 1, 2 or aluminum. For example iron can form Fe2+ or Fe3+ These are said as iron (II) and iron (III) Cu+ and Cu2+ is Copper (I) and Copper (II)

Covalent naming You still drop the ending of the second atom and replace it with the suffix “-ide”. Ionic names ignored the subscript numbers. Covalent does not.

Prefixes prefix meaning *mono- 1 hex- 6 di- 2 hept- 7 tri- 3 oct- 8 tetr- 4 non- 9 pent- 5 dec- 10 * the first atom named does not get the prefix “mono-”, it just keeps its original name!

Examples CO CO2 NI3 P4O6 carbon monoxide carbon dioxide nitrogen triiodide P4O6 tetraphosphorus hexoxide

Continuing I4O9 S2F10 IF7 Si2Cl6 tetriodine nonoxide disulfur decafluoride IF7 Iodine heptafluoride Si2Cl6 disilicon hexachloride