Transcript What Kind of Bonds Hold Elements Together?
How Do We Make Compounds? What is inside the atom? Atom: made of subatomic particles Proton (+) = atomic # : determines the identity of the element Neutron (no charge) Electron (-) Atomic mass = protons + neutrons Periodic Table : arranged by Russian Chemist Dmitri Mendeleev, by atomic # Why do atoms bond? Octet Rule: Every atom wants 8 electrons to fill the valence shell (outer most shell) Ion: Charged atom (Ca+2) Cation: + charged ion Anion: - charged ion Polyatomic Ion: Two or more atoms covalently bonded together to form an ion (SO4-2) What are Ionic, Covalent and Metallic Bonds? Ionic Bond: An electron is transferred from one element to another (metal to nonmetal) Covalent Bond: Electrons are shared (nonmetal to nonmetal) Metallic Bond: Sea of electrons (Metal to Metal) Molecules and Molecular Compounds Properties of molecular compounds Low melting and boiling points Usually gas or liquid Composed of two or more nonmetals O2, O3, H2O How Do We Name Molecular (covalent) Molecules? Name the first element Keep the root of the 2nd element, drop the ending & add “ide” Now add the prefixes The first element does not need the prefix mono Prefixes: Mono (1) Di (2) Tri (3) Tetra (4) Penta (5) Hexa (6) Hepta (7) Octa (8) Nano (9) Deca (10) Name CO2 Name CCl4 Let’s Compare! How Do We Name Ionic Compounds? Name the first element. Use the root of 2nd element and add “ide” (no prefixes) If there is a transition metal, determine the charge and add Roman Numerals If there is a polyatomic ion, name the first element and name the polyatomic ion. Name: CaCl2, FeO, NaOH Exceptions: Some of the transition metals have only one ionic charge: Do not use roman numerals for these: Silver is always 1+ (Ag1+) Cadmium and Zinc are always 2+ (Cd2+ and Zn2+) What are Oxidation Numbers? How do we draw a Lewis Dot Diagram? Determine the number of valence electrons Write the chemical symbol Place a dot for each valence electron around the symbol Writing Chemical Formulas Rules of writing formulas: positive ion (cation) is written first … this is usually a metal negative ion (anion) is written second … this is usually a nonmetal subscripts are used to show how many ions of each part are in the compound. They are used to balance the charge of the ions. Using the Criss Cross Method Determine the oxidation number (charge) on each ion. Write the chemical symbols of each ion (cation1st,anion 2nd) Cross over the numbers ignoring the charges Reduce if necessary HOW DO WE NAME BASES? BASES: USE SAME RULES AS NAMING COMPOUNDS EXAMPLE: NaOH SODIUM HYDROXIDE NOW YOU TRY: Ca(OH)2 KOH Mg(OH)2 CALCIUM HYDROXIDE POTASSIUM HYDROXIDE MAGNESIUM HYDROXIDE HOW DO WE NAME ACIDS? ACIDS: AN ACID’S NAME COMES FROM THE ANION IT PRODUCES WHEN IT DISSOCIATES. HERE ARE SOME RULES; IF THE ANION ENDS IN “IDE” CHANGE IT TO “IC” AND ADD THE WORD “HYDRO” IN FRONT; HYDROGEN CHLORIDE HYDROCHLORIC ACID IF THE ANION ENDS IN “ATE”, CHANGE IT TO “IC” AND DO NOT ADD A PREFIX HCl H2SO4 HYDROGEN SULFATE SULFURIC ACID IF THE NAME ENDS IN “ITE”, CHANGE IT TO “OUS” AND DO NOT ADD A PREFIx H2SO3 HYDROGEN SULFITE SULFUROUS ACID