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Chemical Formulas

Chemical Formulas. A chemical formula is a notation that reveals the atoms that make up a compound. A single atom with a charge. Ex: Mg +2. More than one atom chemically combined, with an overall charge. Monatomic Ions - Polyatomic Ions - Examples you must MEMORIZE :

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Chemical Formulas

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  1. Chemical Formulas A chemical formula is a notation that reveals the atoms that make up a compound.

  2. A single atom with a charge. Ex: Mg +2 More than one atom chemically combined, with an overall charge. • Monatomic Ions - • Polyatomic Ions - Examples you must MEMORIZE: • Phosphate = PO4-3 • Sulfate = SO4-2 • Nitrate = NO3- • Carbonate = CO3-2 • Hydroxide = OH- • Ammonium = NH4+ • Acetate = C2H3O2-

  3. Br2 I2 N2 Cl2 H2 O2 F2 ?? • Diatomic Molecules = Exactly 2 atoms of the same element chemically bonded.(The elements above bond in nature) • Covalent Bonds = Share e- between 2 atoms. (2 non-metals) • Ionic Bonds = Transfer e- from one atom to another. (metal + non-metal) or Polyatomic ions • Cation = Positive ion, formed by losing e-. • Anion = Negative ion, formed by gaining e-. • Writing Formulas for Ionic Compounds 1) Cations MUST be written first. (OH2 wouldn’t be right would it!?) 2) Find the charges, and balance them.. 3) Write the final formula with the appropriate subscripts. (no 1’s) IF you have a Polyatomic Ion, you MAY need parenthesis. 4) Roman Numerals represent the CATION’s positive charge.

  4. THE EXCEPTIONS • Metals tend to ____ electrons. Nonmetals tend to ____ e-. Metalloids act as nonmetals for the most part and _____ electrons. • Metalloids –Silicon and Germanium will either gain or lose depending on what other element it is paired with. If they are paired with a metal, then they will gain electrons and take the -4 charge. If paired with a nonmetal, they take a +4 charge. • d-sublevel – Groups 3 through 15 all have a d-sublevel present containing electrons. Their charges vary, and must show their charge by the use of Roman Numerals. For example, Iron (III) is an iron ion with a +3 charge. 2a)Silver and Zinc – Silver always takes a +1 charge and Zinc always takes a +2 charge. Since this is an “always” situation, the Roman Numeral is not necessary for these two elements. Remember that! 3)Hydrogen willmost often lose its one electron giving it a +1 charge. BUT it also has the ability to gain one to become -1 when reacting with a metal.

  5. Al +3 O -2 Criss-Cross Method – a quicker way, but follow the same rules! Mg+2 NO3-1 = NH4+1 PO4-3 = Al2O3 Mg(NO3)2 (NH4)3PO4

  6. Naming Ionic Compounds • The Cation’s name is written normally. • The Anion’s name changes to “ide”. BUT Polyatomic Ion names do not change. *** ate vs. ite *** NaCl Sodium Chloride Li3N Lithium Nitride Mg(NO3)2 Magnesium Nitrate *** Roman Numerals • Calcium Nitrate • Lithium Carbonate • Ammonium Phosphide • Ammonium Phosphate • Boron Fluoride • Zinc II Hydroxide • Sodium Iodide • Iron III Sulfide

  7. Naming Molecular Compounds (or “Covalent” cmpds) • Don’t forget Hydrogen is NOT a metal!! You must use Prefixes: mono, di, tri, tetra, penta 1 2 3 4 5 Hexa, Hepta, Octa, Nona, Deca • Never begin a molecule’s name with “MONO”. Attempt the following: NO, N2O, N3O4 , CCl , CO2 , P5F3 When finding their formulas FROM their names, you must ignore their charges… Focus only on the prefixes.

  8. ACIDS : Compounds that produce H+ ions when dissolved in Water. Binary Acids: H and only one other element. Begin with “Hydro”. End with the element’s name, but change it’s ending to “ic”. Ternary Acids: H and a Polyatomic Ion. Do NOT use the prefix Hydro.. Only use the Polyatomic Ion’s name, but alter the ending to “ic” - Polyatomic Ion in “ite” form? Ending = “ous” - Polyatomic Ion missing 2 Oxygens? = * HYPO *

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