UNIT 3

1. UNIT 3 Molecules

2. Molecules This is a molecule of water. • Chemistry happens among the electrons. • Bonds occur between atoms as a result of interactions among the electrons. • When the interaction is toshare electrons,the bond is said to becovalentand the entity formed is amolecule. • Formed from nonmetals. H O H H – O – H Structural formula H2O chemical (molecular) formula

3. Properties of Molecular Compounds Properties of Ionic Compounds • held together by covalent bonds • form discrete molecules • soft • low melting point • generally nonconductive • includes all organic compounds • held together by ionic bonds • do NOT form discrete molecules • hard, rigid, brittle • high melting points • conductive when melted or when dissolved in water

4. Diatomic Molecules • When two atoms of the same element form a covalent bond, the result is a diatomic molecule. • Seven nonmetal elements exist as diatomic molecules:H2, N2, O2, F2, Cl2, Br2, I2 H + H H – H (H2) Hydrogen exists naturally as a diatomic molecule.

5. Elements that exist as diatomic molecules

6. Molecular Formulas • A molecular formulashows the number and type of elements in a molecule, e.g., the molecular formula for glucose is C6H12O6. • An empirical formulagives only therelative numberand type of elements, e.g., the empirical formula for glucose is CH2O. • When only one atom of an element is present, no subscript is written. • The molecular formula for water is H2O. • The empirical formula for water is H2O.

7. Nomenclature (Naming) • Inorganic compounds • binary ionic compounds • hydrates • binary molecular compounds • acids with anion name of -ide • acids with anion name of -ate or -ite

8. Naming Binary Molecular Compounds • Name the element farther to the left on the periodic table. (Exception: O is written last unless it’s bonded to F.) • If both elements are in the same group, name the lower one first. • Give the anion name of the second element (-ide ending). • Greek prefixes give the number of each atom in the formula.

9. Nomenclature (Naming) • Inorganic compounds • binary ionic compounds • hydrates • binary molecular compounds • acids with anion name of -ide • acids with anion name of -ate or -ite

10. Acids • Are compounds that produce hydrogen ions (H+)in water. They are molecular compounds that ionize in water. “aq” is short for aqueous which means water. HCl(g)  H+(aq) + Cl- (aq) • or, more correctly, the hydronium ion (H3O+) HCl(g) + H2O H3O+ (aq) + Cl- (aq) In general, acids are compounds of with a formula of HX, H2X, H3X, etc. where X can be an anion from Group 6A or 7A or X can be an oxyanion.

11. Naming Acids with an Anion Name Which Ends in –ide • NOT IN SOLUTION, the name of the acid is just the name of the binary molecular compound: • HCl(g) is hydrogen chloride • IN SOLUTION, • replace hydrogen with hydro- • change –ide to –ic • add the word “acid” • HCl(aq) is hydrochloric acid

12. Nomenclature (Naming) • Inorganic compounds • binary ionic compounds • hydrates • binary molecular compounds • acids with anion name of -ide • acids with anion name of -ate or -ite

13. Naming Ternary (Acids with an Anion That Ends in –ate or -ite) Modify the oxyanion name: • -ateanion becomes –ic • nitrate becomes nitric • -ite anion becomes –ous • nitrite becomes nitrous • then add the word “acid” sulfate: SO42- H2SO4 sulfite: SO32- H2SO3 perchlorate: ClO4- HClO4 chlorate: ClO3- HClO3 chlorite: ClO2- HClO2 hypochlorite: ClO-HClO sulfuric acid sulfurous acid perchloric acid chloric acid chlorous acid hypochlorous acid

14. Names of Common Chemicals

15. Names of Common Chemicals