CHEM 1211K 1st Edition Lecture 6 Outline of Last Lecture I. Chapter 2 Atoms and Elements… ContinuedChapter 3: Molecules, Compound, and Chemical EquationsII. 3.4 An Atomic- Level View of Elements and Compounds1. Atomic elements = exist in single atoms as basic units.2. Molecular elements = exist as molecules (two or more atoms) as basic units. Two atoms = diatomic molecule, more than two = polyatomic molecule3. Molecular compounds = two or more covalently bonded nonmetals.4. Ionic compounds = cation (metals) and anion (nonmetals) bound by ionic bonds III. 3.2 Chemical BondsCompounds are made of atoms held together by bonds.Chemical bonds are forces of attraction between atoms.Two general types of bonding between atoms found in compounds, ionic and covalent.1.Ionic bonds result when electrons have been transferred between atoms, resulting in oppositely charged ions that attract each other (electrostatic forces).Generally found when metal atoms bond to nonmetal atoms (NaCl)Covalent bonds result when two atoms share some of their electrons.Generally found when nonmetal atoms bond together. (H2O, CO)IV. 3.3 Representing Compounds Compounds are generally represented with a chemical formula. All chemical formulas tell what elements are in the compound Use the letter symbol of the element. The number of atoms of each element is written to the right of the element as a subscript (if only one atom, the 1 subscript is not written) (CO2, Na2 S, N2O5). Polyatomic ions are placed in parentheses (if more than one) Example: Sulfate ion, SO42- is a polyatomic ion. Types of chemical formulas:1. Empirical formulaThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.The relative number of atoms of each element in a compound- it does not describe how many atoms, the order of attachment, or the shape- the formulas for ionic compounds are empirical2. Molecular formulaA molecular formula gives the actual number of atoms of each element in a molecule of a compound- it does not describe the order of attachment, or the shape3. Structural formulaA structural formula uses lines to represent covalent bonds and shows how atoms in a molecule are connected or bonded to each other- it does not directly describe the 3-dimensional shape, but an experiencedchemist can make a good guess at it- each line describes the number of electrons shared by the bonded atoms-single line = two shared electrons, a single covalent bond-double line = four shared electrons, a double covalent bond-triple line = six shared electrons, a triple covalent bondV. 3.5 Ionic Compounds: Formulas and Names1. Write the symbol for the metal cation and its charge2. Write the symbol for the nonmetal anion and its charge3. Charge (without sign) becomes subscript for other ion4. Reduce subscripts to smallest whole number ratio5. Check that the sum of the charges of the cations cancels the sum of the anions6. Write systematic name by simply naming the ionsa. if cation is:i. metal with invariant charge = metal name ii. metal with variable charge = metal name(charge)iii. polyatomic ion = name of polyatomic ionb. if anion is:i. nonmetal = stem of nonmetal name + ideii. polyatomic ion = name of polyatomic ionVI. 3.6 Molecular Compounds: Formulas and NamesMolecular compounds form between two or more NONMETALS.1. Write name of first element in formulai. element furthest left and down on the Periodic Tableii. use the full name of the elementiii. Writes name the second element in the formula with an -ide suffix, just like for the anions, however, remember these compounds do not contain ions!2. Use a prefix in front of each name to indicate the number of atomsi. Never use the prefix mono- on the first elementCurrent