1. Chemistry 141
Lecture 5
Friday, September 15, 2017

2. Objectives for today
Understand and use atomic number, mass number, and atomic symbols
Determine atomic weights from isotopic masses and abundances
Identify trends and groups in the periodic table
Distinguish between molecular and ionic compounds
Predict and write chemical formulas
Name chemical compounds

3. Atomic symbol
Isotopes - atoms with the same number of protons (same element) but different numbers of neutrons (mass number)

4. Table of Isotopes

5. An Example: fill in the following chart
Symbol 52Cr
Protons
Neutrons
Electrons
Mass #

6. Average atomic weight
What is the average atomic mass of carbon?

7. Table of Isotopes

8. Periodicity

9. Mendeleev’s Original Periodic Table
(Developed in 1869)
Images from:

10. Modern Periodic Table

11. Types of Formulas

12. Ionic Compounds

13. Your turn
For each of the following pairs, predict the ionic compound they form
Mg and Cl
Fe(III) and O
K and N

14. Chemical Nomenclature
Common names (water, ammonia, etc.)
Ionic compounds
Cations
Group 1 and 2 metals (first 2 columns): same name as element
Transition metals
Add Roman numeral to denote charge: e.g. Fe3+  Iron (III)
Or, use Latin names: e.g. Fe3+  ferric ion, Fe2+  ferrous ion
Molecular cations tend to end in “ium”: e.g. NH4+  ammonium, H3O+  hydronium

15. Chemical Nomenclature
Common names
Ionic compounds
Cations
Anions
Monatomic anions: replace suffix with “ide”
Cl-  chloride
N3-  nitride
Polyatomic anions containing oxygen (oxyanions)
Most “common”  ends in “ate”
One less oxygen than “ate” version  ends in “ite”

16. Chemical Nomenclature
Common names
Ionic compounds
Cations
Anions
Monatomic anions: replace suffix with “ide”
Polyatomic anions containing oxygen (oxyanions)
Most “common”  ends in “ate”
One fewer oxygen than “ate” version  ends in “ite”
One more oxygen than “ate” version  starts with “per” / ends in “ate”
One fewer oxygen than “ite” version  starts with “hypo” / end in “ite”
ClO- = hypochlorite
ClO2- = chlorite
ClO3- = chlorate
ClO4- = perchlorate

17. Chemical Nomenclature
Common names
Ionic compounds
Cations
Anions
Monatomic anions: replace suffix with “ide”
Polyatomic anions containing oxygen (oxyanions)
Oxyanions containing hydrogen
One hydrogen: add “hydrogen” to start of name (add +1 to charge)
Two hydrogens: add “dihydrogen” to start of name (add +2 to charge)
PO43- = phosphate
HPO42- = hydrogen phosphate
H2PO4- = dihydrogen phosphate

18. Chemical Nomenclature
Common names
Ionic compounds
Cations
Anions
Compounds
LiF  ?
aluminum sulfite  ?
FeHPO4  ?

19. Chemical Nomenclature
Common names
Ionic compounds
Cations
Anions
Compounds
Hydrates (some ionic compounds include “waters of hydration”)
FeCl3  iron (III) chloride
FeCl3 • 6H2O  iron (III) chloride hexahydrate

20. Chemical Nomenclature
Common names
Ionic compounds
Acids (anions with hydrogen cations (H+))
From anions ending in “ide”  prefix “hydro”, change “ide” to “ic acid”
From oxyanions
For oxyanions ending in “ate”  change “ate” to “ic acid”
For oxyanions ending in “ite”  change “ite” to “ous acid”
HI  hydroiodic acid
HNO3  nitric acid (H2SO4  sulfuric acid)
HClO  hypochlorous acid

21. Chemical Nomenclature
Common names
Ionic compounds
Acids
Binary molecular compounds
The leftmost (or bottom-most) element on the periodic table goes first
… unless it’s oxygen, which always goes last
… unless oxygen is paired with fluorine, and then it’s first again
The name of the second element is given the “ide” suffix
Use Greek prefixes (mono, di, tri, tetra, etc.) to indicate number of atoms
… but don’t use “mono” for first element
PCl5  phosphorous pentachloride
N2O3  dinitrogen trioxide

22. Chemical Nomenclature
Common names
Ionic compounds
Acids
Binary molecular compounds
Basic organic compounds
Alkanes (contain only C and H): CH4 = methane
Alcohols (contain an OH group): CH3OH = methanol
Organic acids (contain a COOH group): CH3COOH = acetic acid

23. Your turn For each pair below:
Predict the formula of the compound they form
Write the name of the compound
Ca and NO3-
Cr(III) and SO42-
NH4+ and F
H and ClO4-
2 N’s and 5 O’s