Chapter 6 Notes Chemical Names and Formulas

Elements Element – the smallest indivisible unit of matter. Elements are made of just one type of atom. Monatomic Elements – elements that exist naturally as single, separate atoms (Ex: The only really common monatomic elements are the Noble Gases He, Ne, Ar, Kr, Xe, Rn)

Diatomic Elements Diatomic Elements are those whose atoms combine in pairs to form molecules. (ie. they are rarely found as single, separate atoms).

Diatomic Elements You need to memorize these 7 diatomic elements: 1)Hydrogen (gas) - H 2 (Group 1A) 2)Nitrogen (gas) - N 2 (Group 5A) 3)Oxygen (gas) - O 2 (Group 6A) 4)Fluorine (gas) - F 2 (Group 7A) 5)Chlorine (gas) - Cl 2 (Group 7A) 6)Bromine (liquid) - Br 2 (Group 7A) 7)Iodine (crystal) - I 2 (Group 7A) (Note: Group 7A elements are called the Halogens)

Diatomic Molecules Molecules that are made of two atoms of the same element can also be called diatomic molecules: The diatomic elements include: –H 2, N 2, O 2 –First 4 Halogens - F 2, Cl 2, Br 2, I 2

Br I N Cl H O F Bromine Iodine Nitrogen Chlorine Hydrogen Oxygen Fluorine

Tetratomic and Octatomic Elements There are also tetratomic elements… ( Phosphorus – P 4 )

Tetratomic and Octatomic Elements …and octatomic elements ( Sulfur – S 8 )

Compounds and Molecules Compounds – are formed of two or more different types of elements that are chemically combined. Compounds may be either molecular or ionic:

Molecular Compounds Molecular Compounds – are compounds composed of molecules Molecules: are made up of two or more atoms that act as a unit. may be atoms of different elements (molecular compounds) or atoms of the same element (diatomic elements). neutralare electrically neutral.

Molecular Compounds Molecules are the smallest, electrically neutral units of a substance that still have the properties of that substance.

Ionic Compounds Ionic Compounds – are compounds composed of charged particles called ions. Ions – are atoms or groups of atoms that have either gained or lost electrons: (Only electrons can move.)

Ionic Compounds Positive Ions (also called cations) – have lost electrons to have a positive charge. (Metals tend to lose electrons and form positive ions.) Charge is written as a superscript : K+K+ Has lost one electron (no name change for positive ions) Ca 2+ Has lost two electrons

Atoms vs. Ions Negative Ions (also called anions) – have gained electrons to have a negative charge. (Nonmetals tend to gain electrons and form negative ions.) Charge is written as a superscript : F-F- Has gained one electron (-ide is new ending= fluoride) O 2- Gained two electrons (oxide)

Ionic Compounds There is typically one positive metallic ion combined with one negative non-metallic ion in an ionic compound. The base unit of an ionic compound is called a formula unit, not a molecule.

Ionic Compounds are held together by Ionic Bonds

Monatomic and Polyatomic Ions Ions can be monatomic (only one atom) or polyatomic ( many atoms). [See Chart of Ions.] If both ions are monatomic, a binary ionic compound is formed. If one or both ions are polyatomic, a ternary ionic compound with 3 or more elements is formed.

Monatomic and Polyatomic Ions Binary compounds are composed of 2 atoms or ions, while Ternary compounds have 3 or more types of atoms.

Characteristic Molecular Ionic Compound Compound UnitMoleculeFormula Unit Made of:2 or more non- metals 1 metallic ion and 1 non-metallic ion Physical State(s)Solid, Liquid or Gas Solid (Crystals) Melting PointLow (<300 o C)High (>300 o C) Boiling PointLowHigh

Characteristic Molecular Ionic Compound Compound UnitMoleculeFormula Unit Type of BondsCovalent (Share electrons) Ionic Solubility in H 2 O LowHigh (dissolves easily) ConductivityLowHigh (make good electrolytes)

When ionic compounds dissolve in water, they break down into their ions. Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Example: NaCl  Na + + Cl - Electrolytes

Rate of Solvation Dissolving something is a surface phenomenon. A water molecule strikes the surface of the solute and carries a molecule (or ion) away with it. = + = - A solute particle is dissolved when it is surrounded by solvent molecules.

Na + Cl - Na + Cl - Ag + NO O O - NO O O - NO O O - NO O O - Na + + Cl - + Ag + + NO 3 -  Na + + AgCl + NO 3 - Full ionic equation: (all aqueous compounds broken down into ions) Silver chloride (AgCl) precipitates (falls out of solution). NaCl (aq) + AgNO 3 (aq)  AgCl (s) + NaNO 3 (aq)

Bases: Compounds that give OH - when dissolved in water Acids and Bases Na + O H - O H - O H - O H - O H - O H - O H - O H - O H - O H - O H - O H - Example: NaOH  Na + + OH -

Bases: Compounds that give OH - when dissolved in water Acids and Bases Na + O H - O H - O H - O H - O H - O H - Example: NaOH  Na + + OH -

When ionic compounds dissolve in water, they break down into their ions. Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Example: NaCl  Na + + Cl - Electrolytes