1. Atomic number, atomic symbol, mass number, isotopes
Atomic properties
Atomic number, atomic symbol, mass number, isotopes

2. HOW DO WE DESCRIBE AN ATOM
What makes up an atom
Proton (positive charge)
Neutron (neutral charge0
Electron (negative charge)
Now we need to find a way to describe the properties of an individual atom

3. Nucleus Protons and Neutrons are located in the atom’s nucleus.
Electrons- orbit around the nucleus

4. DESCRIBING THE ATOM
Let’s take a look at the periodic tables around the room.
On each periodic table are several things
Symbol for the element
Name of the element
Numbers that describe the element

5. HOW DO WE NAME AN ELEMENT
The first thing we will examine is the naming of elements
Finding the names of elements is like doing a giant word search
EXAMPLE: What is the name of the element with the symbol He?

6. ANSWER
He is the symbol for the element
HELIUM

7. TRY THESE Br Li Zn B Ag K

8. ANSWERS Br - Bromine Li - Lithium Zn - Zinc B - Boron Ag - Silver
K – Potassium
Let’s look at #5 and #6

9. FIND THE SYMBOL FROM THE NAME
It’s usually easier to find the name of the element when you have the symbol. It’s harder to find the symbol when you have the name.
Try these:
Mercury
Xenon
Iron

10. REMINDER: For your periodic table
ANSWERS
Mercury - Hg
Xenon - Xe
Iron – Fe
REMINDER: For your periodic table
You may use this on your quizzes
You must fill in your own information

11. WHAT DEFINES AN ATOM One particle defines what an atom (or element is)
This particle is the PROTON
The number of protons in an atom tells us what element it is.

12. ATOMIC NUMBER Atomic number: the number of protons in an atom
Example: Find Hydrogen (H) on your periodic table
The atomic number of hydrogen is 1.
What is the atomic number for He?

13. ATOMIC NUMBER
The periodic table is arranged in order of increasing atomic number.
Find the atomic number for these:
Sulfur
Uranium
Gold

14. ATOMIC NUMBER Sulfur - 16 Uranium - 92 Gold – 79
If you ever change the number of protons, you change the atom into a different element.

15. MASS NUMBER
Mass number: the sum of an element’s protons and neutrons. Remember, electrons don’t have an atomic mass
On your periodic table, this is found below the symbol of the element
EXAMPLE: The mass number for H (hydrogen) is 1.008

16. UNITS The unit for the mass unit is the atomic mass unit (amu)
Therefore:
Hydrogen has a mass number of
1.008 amu

17. FIND THE MASS NUMBER
Find the mass number for the following: Cl Pd Sr

18. Shells/ Orbitals/ Energy Levels
The electrons orbit around the nucleus of the atom
These area are called:
shells,
or orbitals,
or energy levels

19. Valence Electron
Valence electrons are the electrons in the outer most shell(energy level/ orbital) of an atom.

20. End of 1st Day

21. MASS NUMBER AND ISOTOPES
Notice that not all the mass numbers are whole numbers
A lot of them have decimals
WHY?

22. Average Atomic Mass
To calculate the average atomic mass, multiply the fraction by the mass number for each isotope, then add them together. 

23. Average Atomic Mass
Average atomic mass = f 1M 1 + f 2M 2  f nM n where f is the fraction or decimal representing the natural abundance of the isotope and M is the mass number (weight) of the isotope.. 

24. Average Atomic Mass
To calculate the average atomic mass, multiply the percentage in decimal form by the mass number for each isotope, then add them together. 

25. Average Atomic Mass (12.000000) (0.9890) + (13.003355) (0.0110)
Example:
( ) (0.9890)
+ ( ) (0.0110)
= amu
mass number
exact weight
percent abundance 12
98.90 13
1.10

26. ISOTOPES
The reason is that not every atom in an element has the same number of neutrons
ISOTOPE: atoms of the same element with different numbers of neutrons
Ex: C-12 and C-14
Isotopes of atoms is what is responsible for radiation
The mass number is an average of all the different isotope masses

27. SYMBOLS How do we show how many protons and neutrons are in a symbol.
EXAMPLE:
An element has 10 protons and 10 neutrons, how do we show it?
First, what is the element?

28. Number of protons + neutrons
SYMBOLS Ne
Number of protons + neutrons 20 10
Number of protons

29. WRITE THE SYMBOL FOR THESE
35 protons and 45 neutrons
40 protons and 51 neutrons
78 protons and 117 neutrons

30. HOW MANY PROTONS AND NEUTRONS
40Ar 18
56Fe 26
238U