2An Element is a Pure substance containing only one kind of atom. eLEMENTSAn Element is a Pure substance containing only one kind of atom.
32 or more elements chemically combined Creates a new substance CompoundsCompounds:2 or more elements chemically combinedCreates a new substance
4substance made of two or more atoms moleculesubstance made of two or more atomsCan be the same element or different elements
5Compounds, molecules, and elements KAuFePbI2O2CH4H2OC6H12O6CaCO3Compare and Contrast Molecules and CompoundsWhat do you notice?Compounds are 2 or more different atomsMolecules are 2 or more atoms (can be the same or different)
6Chemical CompoundsTwo or more elements chemically combined and Formed by chemical bonds between atoms. Ionic bonds: form ions – Covalent bonds: form molecules Compounds Have unique chemical and physical properties. The properties of compounds are very different from the properties of the individual elements.
7Chemical FormulasChemical formulas describe compounds and list the atoms that are present in the compound.NaCl – Sodium chloride (salt) – Na – Sodium, Cl - ChlorineH2O – Dihydrogen monoxide (water) – H – Hydrogen, O - Oxygen –CO2 – Carbon dioxide – C – Carbon, O - Oxygen
8Subscripts H2O – 2 Hydrogen, 1 Oxygen Numbers written below and to the right of a chemical symbol in a formula.H2O – 2 Hydrogen, 1 OxygenTells how many atoms of an element are in each molecule.Only used if more than one atom is present.CAN Never be changed in a formula
9C9H8O4 C = Carbon – 9 atoms H = Hydrogen – 8 atoms O = Oxygen – 4 atoms3 elements total atoms
10H2SO4 H = Hydrogen – 2 atoms S = Sulfur – 1 atom O = Oxygen – 4 atoms 3 elements atoms
12Coefficients # placed in front of a chemical symbol or formula Identifies the # of molecules of a substance2H2O = 2 molecules of H2O2FeO3 = 2 molecules of FeO3
13Coefficients X Subscripts To determine the number of atoms using coefficients you multiply the coefficient with the subscript.2H2O - 2 molecules of H2O= 4 Hydrogen atoms and 2 Oxygen atoms
142Fe2O3 2 Molecules of Fe2O3 = 2 X 2 = 4 Fe (iron) atoms 2 X 3 = 6 O (oxygen) atoms
15Coefficient Practice: How many atoms are present? Carbon: 2 atomsHydrogen: 8 atomsHydrogen: 4 atomsOxygen: 4 atomsHydrogen: 2 atomsChlorine: 2 atoms
16Using ParenthesesMultiply the subscript with each element in parentheses.Al2(SO4)3Al = 2 atoms of AluminumS = 3 X 1 = 3 atoms of SulfurO = 4 X 3 = 12 atoms of Oxygen
17(CH3)2CHOH C = Carbon = 2x1 = 2+1 = 3 carbon atoms H = Hydrogen = 3x2 = 6+2 = 8 Hydrogen atomsO = Oxygen = only 1 Oxygen atom
18Parentheses H H Ca O O Calcium: 1 atom Oxygen: 2 atoms Hydrogen: 2 atoms
19Chemical Formulas KNO3 NH4Cl Check out Potassium Nitrate… How many atoms of nitrogen are present?How many atoms of oxygen are present?How many atoms of potassium are present?Now Ammonium Chloride…NH4ClHow many atoms of chlorine are present?How many atoms of hydrogen are present?How many atoms of nitrogen are present?
20Chemical Formulas Mg(OH)2 Let’s take it up a notch… Check out Magnesium Hydroxide…Mg(OH)2Some formulas involve parenthesis. When this happens, multiply EVERYTHING inside the parenthesis by the subscript that is outside. The subscript outside can NEVER be changed.How many atoms of magnesium are present?How many atoms of hydrogen are present?How many atoms of oxygen are present?
21Chemical Formulas Ca3(PO4)2 Check out Calcium Phosphate… How many atoms of phosphorous are present?How many atoms of calcium are present?How many atoms of oxygen are present?
22Chemical Formulas 6C9H8O4 Let’s take it up a notch again… Check out the formula for aspirin…6C9H8O4The 6 in front of the formula is a coefficient. It tells how many molecules of a compound are present. You multiply the coefficient by EVERYTHING that comes after it.How many atoms of oxygen are present?How many atoms of hydrogen are present?How many atoms of carbon are present?