1. Atomic Number, Mass Number, and Isotopes
Ms. Knick
Chem 1A
HAHS

2. Subatomic Particles There are three subatomic particles:
1. Electrons (negatively charged)
2. Protons (positively charged)
3. Neutrons (neutral = no charge)

3. Locations of the Subatomic Particles
Neutrons and protons are located in the nucleus
Electrons are located in orbitals surrounding the nucleus (electron cloud)

4. How many protons, electrons, and neutrons?
Look at your periodic table.

5. Atomic Number
Is specific for each element (each element has its own atomic number)
Whole number at the top of the element tile
Periodic table is arranged according to increasing atomic number
Never changes for a particular atom
The atomic number represents the number of protons.
It also represents the number of electrons because an atom is neutral
The atomic number of carbon is 6. Carbon has 6 protons and 6 electrons.

6. Check your understanding!
How many protons does titanium have? How many electrons?
How many protons does tungsten have? How many electrons?
How many protons does radon have? How many electrons?

7. Atomic Mass Decimal number at the bottom of the tile
Units are atomic mass units (abbreviated as amu)
Represents the total number of protons and neutrons in the atom.
Carbon’s atomic mass is 12 amu. It has a total of 12 protons and neutrons.

8. To determine the number of neutrons
Subtract!
Number of neutrons = atomic mass – atomic number
9 – 4 =
5 neutrons

9. Check your understanding!
How many neutrons does platinum have?
How many neutrons does manganese have?
How many neutrons does mercury have?

10. Protons, Electrons, and Neutrons
Potassium?
Protons= ______ Electrons = ______ Neutrons=_______
Nickel?
Copper?

11. Ions An atom with a charge. Two types:
Cation = positively charged (Example: Mg2+)
Anion = negatively charged (Example: F-1)

12. Ions and Electrons
The charge of an atom affects the number of electrons.
Cations are positive. They are losing electrons and thereby are becoming MORE POSITIVE.
Anions are negative. They are gaining electrons and thereby are becoming MORE NEGATIVE.

13. Example
How many protons, electrons, and neutrons?
O2-
Al3+ F-
Mg2+

14. Isotopes
Isotopes are atoms that have the same number of protons but a different number of neutrons.
As a result, isotopes of the same element have a different atomic mass.
This is why the atomic mass, is a decimal number. The atomic mass is an average of all isotopes of a particular element.

15. Isotopes of Hydrogen

16. Formula for Average Atomic Mass

17. Examples: Skip 6 lines in between each example problem:
Example #1: The natural abundance for boron isotopes is: 19.9% 10B ( amu) and 80.1% 11B (11.009amu). Calculate the atomic mass of boron. 
Example #2: Silicon has three isotopes. The data is below. What is the average atomic mass?
Isotope 1
27.98 amu
92.21%
Isotope 2
28.98 amu
4.70%
Isotope 3
29.97amu
3.09%

18. Color Code the Periodic Table! Please make it neat and clear to read!
Color the square for Hydrogen pink.
Lightly color all metals yellow.
Place black dots in the squares of all alkali metals.
Draw a horizontal line across each box in the group of alkaline earth metals.
Draw a diagonal line across each box of all transition metals.
Color the metalloids purple.
Color the nonmetals orange.
Draw small brown circles in each box of the halogens.
Draw checkerboard lines through all the boxes of the noble gases.
Color all the lanthanides red.
Color all the actinides green.
 When you are finished, make a NEAT key underneath the title of your periodic table.