1. Atoms and Bonding Review

2. Valence Electrons highest energy level held most loosly number of valence electrons determines many properties, especially how it bonds Electron Dot diagram Includes chemical symbol and number of valence electrons Chemical Bond Stability comes with 8 valence electrons Atoms typically react in a way that will make them stable ex. Group 17 bonding with group 1 chemical bond is the force of attractions that holds two atoms together

3. Periodic Table Elements location can tell you how many valence electrons it has and how reactive that element is Atomic number increases from left to right First energy level holds 2 valence electrons All other hold up to 8 Inert Gases 8 valence electrons (except Helium has 2) full energy level so they are stable Reactive Elements Halogens - 7 valence electrons, need 1 more – highly reactive Alkali Metals – 1 valence electron, want to get rid of it, highly reactive

4. Ionic Bonds Ion An atom or group of atoms that has an electric charge Lose an electron atom becomes positive Gain an electron atom becomes negative Polyatomic Ions ions made of more than one atom Ionic Bonds attractions between oppositely charged ions (attraction between opposites – negative an positive) Takes or transfers electrons

5. Chemical Formula chemical symbols and subscripts that show the ratio of the elements when ionic compounds form, negative and positive charges balance out subscript – tells you how many atoms of that element are in the compound Naming Ionic Compounds name of the positive ion comes first (usually the metal), followed by the negative ion

6. Properties of Ionic Compounds Hard Brittle Solid High melting point – because bonds are so strong Melted or dissolved in water – conduct electricity Crystal = orderly 3D arrangement

7. Covalent Bonds Bond forms when there is a sharing of electrons Usually with nonmetals Held together by the attraction of each atom’s nucleus for the electrons Molecule – neutral groups of atoms joined by covalent bonds Double and triple bonds – share 2 or 3 pairs of electrons

8. Covalent Bond Properties Lower melting and boiling point – bond is not as strong Do not conduct electric current when melted or dissolved Unequal sharing of electrons cause slight electric charge Polar bond – electrons NOT shared equally Nonpolar bond – electrons shared equally Depending how the atoms arranged will determine if polar or not ex. Water H are on one side of O – O pulls in one direction Carbon Dioxide C is in middle, O’s are on opposite sides pulling away from C therefore the overall pull is neutral

9. Metallic Bonds Alloy – mixture of 2 or more elements where at least 1 is a metal. They are stronger and less reactive than pure metals Metal atoms combine in regular patterns where the valence electrons are free to move from atom to atom Sea of electrons explains properties of metallic bonding

10. Properties of Metallic Bonding Malleable – pound into shapes Ductility – draw into long wires Luster – ability to shine High electrical conductivity High thermal conductivity