1. The Atom

4. Theories change over time as new evidence is discovered
Theories change over time as new evidence is discovered. They are not thrown out, they are modified and improved!

5. Remember-The Electron is SO very TINY that it is not included in the atomic mass!

6. Atomic Number = # of protons +
Atomic Mass = mass of the nucleus (Protons + Neutrons)

7. You try What is the Atomic number? How many protons?
How many electrons?
Atomic Mass?
How many Neutrons?

8. You try What is the Atomic number? 13 How many protons? 13
How many electrons? 13
Atomic Mass?
How many Neutrons? 14
(Mass – Protons = Neutrons because Neutrons and Protons make up the mass of the atom!)

9. Each grain of sand is made of atoms
No….silly….you cannot see an atom with a hand lens.
The nucleus contains protons and NEUTRONS, not electrons.
Yes…slide before this. Atomic # of Helium is 2 because there are 2 protons.
No-Helium’s mass is made up of protons and neutrons, so mass is 4.
However, once something is SMALLER than an atom, it no longer retains the properties of that atom. Example, the element gold is made up of gold atoms, BUT if we break apart a gold atom, its protons, neutrons, and electrons do not have properties of gold.

10. Atomic # =
# of protons = # of electrons
(since they are equal + 11 and -11, net charge = 0)
Mass # =
# of protons + # of neutrons