1. ISOTOPIC NOTATION isotopes are atoms with the same number of protons but different number of neutrons A
Z X
A = mass number
(the total number of protons + neutrons)
Z = atomic number
(the total number of protons)
X = element symbol

3. READING ISOTOPIC NOTATION46
21 Sc
46 = mass number
(the total number of protons (21) + neutrons (25)
21 = atomic number
(the total number of protons (21))
Sc = element symbol
In a neutral atom, the number of electrons (21) is equal to the number of protons.

4. PRACTICE PROBLEMS 15N 35P 62Cu2+ 76Se3- 7 8 7 15 20 15 27 29 33 42 34
# protons = ____ # neutrons= ____ #electrons = ___
35P
# p = ____ # n= ____ #e- = ___
62Cu2+
76Se3-
# p = ____ # n= ____ #e- = ___ 7 8 7 15 20 15 27 29 33 42 34 37

5. Writing ISOTOPIC NOTATION
Write the symbol for the atom with an atomic number of 21 and a mass number of 48.
Give the complete chemical notation for the nuclide with 23 protons, 26 neutrons and 20 electrons.
Write the isotopic notation for
Z = 46 A = 110
An atom containing 24 protons, 28 neutrons, and 21 electrons
Titanium-50
48 Sc
49V3+
110Pd
52Cr3+
50Ti

6. PRACTICE PROBLEMS 196 Pt4+ # p = _____ # n = _____ #e- = _____
mass number = ________ atomic number = _______
atomic mass = ________ name of element = _______
2. Indicate the appropriate average atomic mass of an element with 30 protons, 30 neutrons, and 28 electrons. 74
118 78 78
196
195.1 amu
platinum
65.39 amu

7. Atomic Mass
The atomic mass of an element represents the average mass of all the isotopes found in nature. No element exists with only one possible isotope. Hydrogen has the smallest number of isotopes: 1H protium, 2H deuterium, 3H tritium. Its atomic mass is amu (atomic mass units). The atomic mass is calculated by adding the % of 1H mass found in nature to the % of 2H mass found in nature plus the % of 3H mass.
% 1H + % 2H + % 3H = average mass (atomic mass)
Generally the formula used is:
% A + % B + % C… = atomic mass.
An instrument called the mass spectrometer is generally used to determine the percentages and individual masses of each isotope.

8. Now look at the periodic table to verify the answer.
Atomic Mass
Silver is found to have two stable isotopes, one has an atomic mass of amu and the other weighs amu. The first isotope represents % of the mass of the element and the second represents %. What is the atomic mass of the element silver?
The equation to use is %X + % Y = average
And remember to turn your percents into fractions before multiplying.
(0.5182) amu + (0.4818) amu =?
amu amu =?
amu !!
Now look at the periodic table to verify the answer.

9. PRACTICE PROBLEMS # 8
1. A sample of neon contains three isotopes, neon-20 (with an isotopic mass of amu), neon-21 ( amu) and neon-22 ( amu). The natural abundances of these isotopes are 90.92%, %, and 8.82 %. Calculate the atomic weight of neon.
2. There are only two naturally occuring isotopes of copper, 63Cu and 65Cu. Copper has an atomic mass of amu. Which is the most abundance isotope?
3. There are only two naturally occuring isotopes of gallium, 69Ga and 71Ga. Which is the most abundance isotope?
20.17 amu
65Cu = 30% & 63Cu = 70%
69Ga = 60% and 71Ga = 40%

10. GROUP STUDY PROBLEM #8
_______1. The element with atomic number 53 contains
a) 53 neutrons b) 53 protons C) 26 neutrons & 27 protons d) 26 protons & 27 neutrons
108
_______2. The number of neutrons in an atom of Ag is
a) b) c) d) 61 27
_______3. The number of electrons in an ion of 13 Al3+ is
a) b) c) d) 14
Calculators
_______4. What is the relative atomic mass of boron if two stable isotopes of boron have the following mass and abundance:
amu (19.91%) & (80.09%)
a) amu b) amu c) amu d) amu