1. Chapter 3 Chemical Foundations: Elements, Atoms, and Ions
Atoms, Ions and Isotopes

2. Learning Targets
You will learn about atoms, ions and isotopes.

3. Symbols to be familiar with:
The atom
Symbols to be familiar with:
Protons = p+
Neutrons = n0
Electrons = e-
Atoms are always neutral
Neutral = Same number of protons and electrons

4. The symbol for an atom A Z A = the mass number (# p+ + n0)X Z
A = the mass number (# p+ + n0)
X = symbol of element
Z = the atomic number (number of protons)

5. Funnies 
Two molecules are walking down the street; one bumps into the other and says:
"Oh, my fault, you okay?”
The Second Molecule says: "No, I'm not ok, I've lost an electron!" So the first molecule says: "Are you sure" the second molecule answers, "I'm positive!"

6. Calculating mass number
1 equation rearranged:
A = Z + neutrons
Mass Number = # of protons + # neutrons OR
A – neutrons = Z
Mass number – neutrons = # protons
A – Z = neutrons
Mass number - # protons = # neutrons

7. Isotopes
Isotopes are atoms that have the same number of protons, different number of neutrons
Often represented as:
element name – mass #.
(Example: carbon – 14)

8. Practice
Give the number of protons, neutrons and electrons in the atom symbolized by
201 Hg 80
Give the symbol to represent the following information:
The cesium atom with a mass number of 132

9. Try on your own
Give the number of protons, neutrons and electrons in the atom symbolized by 90 Sr 38
Strontium-90 occurs in fallout from nuclear testing. It can accumulate in bone marrow and may cause leukemia and bone cancer.
Give the symbol to represent the following information:
The iron atom with a mass number of 56

10. Ions Ions are atoms with a charge
cations (positively charged ion)
anions (negatively charged ion)
Ions have a charge because they are gaining or losing electrons from their neutral atom
Symbol is element symbol with the ion charge as a superscript (Example: Ca2+)
Usually formed when metals combine with nonmetals

11. Ions that certain groups form on the periodic table

12. Ions that certain groups form on the periodic table
Groups have similar characteristics – one being how many electrons are lost or gained from the neutral atom
Ions have unequal numbers of protons and electrons. Different from atoms because numbers are equal.
Group 1: 1+
Group 2: 2 +
Group 3 or 13: (there are exceptions)
Group 4 or 14: gives or takes electrons
Group 5 or 15: 3- (there are exceptions)
Group 6 or 16: 2-
Group 7 or 17: 1-
**know these charges and put on periodic table

13. Examples
For each of the following ions, indicate the total number of protons and electrons in the ion (#46 in your book)
A. Co2+ E. S2-
B. Co3+ F. Sr2+
C. Cl- G. Al3+
D. K+ H. P3-

14. Examples-Answers A. 27 p, 25 e B. 27 p, 24 e
C. 17 p, 18 e D. 19 p, 18, e
E. 16 p, 18 e F. 38 p, 36 e
G. 13 p, 10 e H. 15 p, 18 e

15. Homework
Atomic Structure Worksheet DUE MONDAY