1. Isotopes, Atomic Numbers, and Mass Numbers
Atomic number (Z) = number of protons in the nucleus.
Mass number (A) = total number of nucleons in the nucleus (i.e., protons and neutrons).
By convention, for element X, we write ZAX.
Isotopes have the same Z but different A.

2. The Atomic Mass Scale 1H weighs 1.6735 x 10-24 g
and 16O x g.
We define: mass of 12C = exactly 12 amu.
Using atomic mass units:
1 amu = x g
1 g = x 1023 amu

3. Isotope Calculation Review
The atomic masses listed on the periodic table are average atomic masses
They are determined by calculating the weighted mean.
Average atomic mass =
Σ (isotope mass)( relative abundance)

4. Isotope Calculations Example 1
Atomic Mass
Relative Abundance
28Si
27.976 %
29Si
28.976
4.6832%
30Si
29.973
3.0872%
Using the isotope information for Silicon. Find the average atomic mass.

5. Isotope Calculations Example 2
Naming and Formula Writing
Isotope Calculations Example 2
Silver consists of two isotopes 107Ag and 109Ag. Its average atomic mass is Calculate the percentage of each isotope in naturally occurring silver. (Assume that the masses are and respectively.)

6. Naming & Formula Writing
Naming and Formula Writing
Naming & Formula Writing

7. Naming and Formula Writing
Background: Periodic Table
Some of the groups in the periodic table are given special names.
These names indicate the similarities between group members:
Group 1: Alkali metals.
Group 2: Alkaline earth metals.
Group 16: Chalcogens.
Group 17: Halogens.
Group 18: Noble gases.

8. Background: Molecules
Naming and Formula Writing
Background: Molecules
Definition: a group of two or more atoms held together by a covalent chemical bond.
Typically a covalent bond is between two non-metals (This is a general rule of thumb.)
Examples: Water (H2O), Bromine (Br2), ammonia (NH3), Vinegar (HC2H3O)

9. Naming and Formula Writing
Background: Ions
Definition: An atom or group of atoms that have an overall positive or negative charge
Monatomic ions: atoms that have lost or gained electrons.
Charge related to position on Periodic Table for monoatomic ions
Cation: Positive ion (Typically metal)
Anion: Negative ion (Typically non-metal)

10. Naming and Formula Writing
Background: Formulas
Empirical formula: shows the lowest whole number ratio of the atoms in the compound.
Molecular formula: shows the exact number of each kind of atom in the compound.
Structural formula: shows how the atoms in the molecule are bonded together

11. Background: Formula of Molecular Compounds
Naming and Formula Writing
Background: Formula of Molecular Compounds

12. Background Practice: Benzene
Naming and Formula Writing
Background Practice: Benzene C H ? ?
Empirical Formula
Structural Formula
Molecular Formula

13. Background: Predicting Charges
Naming and Formula Writing
Background: Predicting Charges

14. Naming and Formula Writing
I. Ionic Compounds
Are formed because of the strong electrostatic attraction between cations and anions.
Binary ionic compounds are always between a metal and a non-metal.
Other ionic compounds must contain a polyatomic ion
Examples: Table salt (NaCl), baking soda (NaHCO3), Epsom salts (MgSO4)

15. Naming and Formula Writing
Common Cation Charges

16. Naming Ionic Compounds
Naming and Formula Writing
Naming Ionic Compounds
Simply write the name of the cation first
Group 1,2 elements, Al3+, Zn2+, Ag1+, Ga3+, In3+ are simply named
Polyatomic cations are also simply named
Other metals can have more than one charge, so the name must indicate the charge with a roman numeral.
Cu1+ is copper(I)
Cu2+ is copper(II)
Then write the name of the anion
Polyatomic anions are simply named
Remember the name of a monatomic anion ends in –ide.
oxygen forms the anion oxide (O2-)
nitrogen forms the anion nitride (N3-)

17. Naming and Formula Writing
Lots of examples
KCl Potassium chloride
Mg 3N2 Magnesium nitride
Na2SO4 Sodium sulfate
(NH4)2CO3 Ammonium carbonate
CuO Copper(II)oxide
Cu2O Copper(I)oxide
FePO4 Iron(III)phosphate

18. Formula Writing Ionic Compounds
Naming and Formula Writing
Formula Writing Ionic Compounds
Identify the compound as ionic
Find the formula and charge of the cation and the anion.
Use subscripts to indicate the number of each ion needed to have an overall neutral charge. “Drop and Swap”
Reduce the subscripts to the lowest whole number ratio.

19. Naming and Formula Writing
Ionic Naming Examples
Sodium fluoride Na1+ F1-
NaF
Calcium nitride Ca2+ N3-
Ca3N2
Barium nitrite Ba2+ NO21-
Ba(NO2)2
Lead(II)hydroxide Pb2+ OH1-
Pb(OH)2
Manganese (IV) Sulfide Mn4+ S2-
Mn2S4  MnS2

20. Naming and Formula Writing
Now You Try
Name
Formula
Silver chloride
Zinc nitrate
Ammonium hydroxide
Tin(II)sulfite
Al2O3
Fe2(SO4)3
MnO
NaNO3

21. Naming and Formula Writing
Hydrates
Hydrates are compounds that contain discrete water molecules as part of the crystal lattice structure.
CuSO4•5H2O is called copper(II)sulfate pentahydrate.
You will use the Greek prefixes to indicate the number of water molecules in the compound.

22. Prefixes for Hydrates Number Prefix 1 mono 2 di 3 tri 4 tetra 5 penta6
hexa 7
hepta 8
octa 9
nona 10
deca

23. Naming Polyatomic Ions With Oxygen
Naming and Formula Writing
Naming Polyatomic Ions With Oxygen

24. Naming and Formula Writing
Example
Selenate is SeO42-
What is selenite?
Answer:
Bromate is BrO3-
What is hypobromite?

25. Oxygen and Hydrogen Containing Polyatomic Compounds
Naming and Formula Writing
Oxygen and Hydrogen Containing Polyatomic Compounds
Polyatomic anions containing oxygen with additional hydrogens are named by adding hydrogen or bi- (one H+), dihydrogen (two H+), etc., to the name as follows:
CO32- is the carbonate anion
HCO3- is the hydrogen carbonate (or bicarbonate) anion.
H2PO4- is the dihydrogen phosphate anion.

26. Naming and Formula Writing
II. Naming Acids

27. II. Naming Acids A helpful mnemonic for naming oxyacids
I don’t feel well because I “ate” something “ic”ky!
For example carbonate (CO32-) makes carbonic acid

28. Naming and Formula Writing
Practice With Acids
HCN
HNO3
HNO2
HClO4
HClO3
H2SO3
HCl
HBr HI

29. III. Binary Molecular Diatomic Elements
Naming and Formula Writing
III. Binary Molecular Diatomic Elements

30. More about the Elements
Naming and Formula Writing
More about the Elements
Allotropes: Different forms of the same element
Some well know allotropes are:
Carbon: Graphite, Diamond, “Bucky Balls”
Oxygen: Oxygen gas, Ozone
Tin: White (metallic tin), Gray Tin
Diatomic Elements: Elements that exist as molecules with two atoms.

31. Naming and Formula Writing
Empirical formula: shows the lowest whole number ratio of the atoms in the compound.
Molecular formula: shows the exact number of each kind of atom in the compound.
Structural formula: shows how the atoms in the molecule are bonded together

32. Formula Writing and Naming Binary Molecular Compounds
Naming and Formula Writing
Formula Writing and Naming Binary Molecular Compounds
Identify the molecular compound because there are two non-metals.
The most metallic element is usually written first (i.e., the one to the farthest left on the periodic table). Exception: NH3.
If both elements are in the same group, the lower one is written first.
Use prefixes to indicate the number of a particular atom in the compound.
mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca.
Truncate the name of the last element and then add –ide
Example: NCl3 is nitrogen trichloride

33. Naming and Formula Writing
Now you Try
Name
Formula
XeF6
P2O3
Tetraphosphorus decoxide
Nitrogen triiodide