1. The Structure of an Atom

2. Atoms
All atoms are made up of protons, neutrons and electrons- these are subatomic particles
Protons are positively charged particles found in the nucleus of an atom
Neutrons are neutral particles also in the nucleus of an atom
Electrons are negatively charged particles that orbit around the nucleus in an electron cloud
These subatomic particles can be distinguished by mass, charge and location in an atom

3. Atomic Number and Mass Number
Atomic Number- the number of protons in an element
Atomic # identifies an element
Atoms of different elements have different atomic numbers
Since elements are electrically neutral, the # of protons equals the # of electrons
Mass Number- total number of protons and neutrons in an element
p+ + n0= mass number

4. Isotopes
In Dalton’s atomic theory, all atoms of a given element are the same
They have the same number of protons and electrons
Atoms of the same element can have different number of neutrons – these are called isotopes
Same atomic number, different mass number

5. Reading Information on Periodic Table
Atomic Number
Symbol
Name 6 C
Carbon
12.011
*Memorize*
Atomic # = # of protons
# of protons = # of electrons
Atomic mass = # of protons + # of neutrons
Average Atomic Mass
Why is the mass of carbon a decimal?

6. Practice What is the atomic number of Li? How may electrons are in Li?
What is the mass number?
How many neutrons are in Li? 3 Li
Lithium 6
Look at the periodic table in the back of you book:
What is the name of an element that has 47 protons?

7. With your partner
Pg 112 in your book
#8 and 9
Hand in