1. Wake-up
Explain the relationship between the following: atomic number, mass number, protons, neutrons, and electrons.
How do you find the number of electrons of an element?
How do you find the number of neutrons of an element?

2. Isotopes and Relative Abundance
What is an isotope?
What is relative abundance?

3. Examine the information of hydrogen below and answer the following questions. Do not round the mass number!

4. What element and chemical symbol is shown?
Hydrogen and H

5. What is the atomic number for this element?1

6. What is the atomic mass for this element? Don’t round

7. List the number of protons, electrons, and neutrons (in that order)
1 p+, 1 e-, 0 n0

8. What is an ISOTOPE?
Isotope = atoms that have the same number of PROTONS but different number of NEUTRONS.
Chemically alike but with varying mass numbers

9. APPLE VARITIES

10. Examine the mass number of the various elements on the periodic table
Examine the mass number of the various elements on the periodic table. Very few are even. This is due to isotopes. The mass number is better known as the Atomic Mass or Atomic Unit. This number represents the AVERAGE mass of all the naturally occurring isotopes of an element.

11. Atomic Mass
Average of the masses of an elements (atom) naturally occurring isotopes

12. Relative abundance of elements on Earth’s surface
The abundance isotopes of an element as naturally found on a planet (%)
Relative abundance of elements on Earth’s surface

13. Hyphen notation: Write the element name and the mass number
Review Notations
Hyphen notation: Write the element name and the mass number
Hydrogen - 1

14. Nuclear notation: See diagram below
Review Notations
Nuclear notation: See diagram below

15. In other words, all the isotopes of the same element (atom) have the SAME   but DIFFERENT
Atomic Number (p+ and e-)
Mass Number (specifically n0)

16. (Most common isotope of Hydrogen has a 99.985% relative abundance)
Isotope: Hydrogen-1
Name: Protium
(Most common isotope of Hydrogen has a % relative abundance)

17. Isotope: Hydrogen-1
# of Protons: 1
# of Electrons: 1
# of Neutrons: 0

18. (Relative Abundance: 0.015% of Hydrogen)
Isotope: Hydrogen-2
Name: Deuterium
(Relative Abundance: 0.015% of Hydrogen)

19. Isotope: Hydrogen-2
# of Protons: 1
# of Electrons: 1
# of Neutrons: 1

20. (Relative Abundance: Very small amounts of Hydrogen)
Isotope: Hydrogen-3
Name: Tritium
(Relative Abundance: Very small amounts of Hydrogen)

21. Isotope: Hydrogen-3
# of Protons: 1
# of Electrons: 1
# of Neutrons: 2

22. Calculating Average Atomic Mass
Formula:
(% abundance #1)(Mass #1) + (% abundance #2)(Mass #2)
100

23. Calculating Average Atomic Mass #1
You have a box containing two sizes of marbles.
25% of the marbles have a mass of 2.0 g.
75% of the marbles have a mass of 3.0 g.
Calculate the average weight of the marble.

24. Example #2: Rubidium has two common isotopes, 85Rb and 87Rb
Example #2: Rubidium has two common isotopes, 85Rb and 87Rb. If the abundance of 85Rb is 72.2% and the abundance of 87Rb is 27.8%, what is the average atomic mass of rubidium?

25. Example #3: The element boron has two stable isotopes
Example #3: The element boron has two stable isotopes. Boron-10 has an atomic mass of and a percentage in nature of 19.78% The atomic mass of boron-11 is and its percentage in nature is 80.22% What is the average atomic mass for boron?