Atoms

1. Chapter 9
Lesson 2

2. Parts of an Atom
Proton
Neutron
Electron
Nucleus

3. Atoms
Electron or e- / Charge 1- / Cloud around nucleus
Proton or p / Charge 1+ / Nucleus
Neutron or n / Charge 0 / Nucleus

4. Atoms
Atomic number: the number of protons in an atom of an
element
Different elements have different atomic numbers
Carbon is 6 / Oxygen is 8 / Nitrogen is 7

6. Isotope
Atoms of the same element that have different numbers
of neutrons
Example: Carbon

7. Mass Number
The sum of the number of protons and neutrons in an
atom
Mass number = number of protons + number of
neutrons

8. Isotope
Carbon-12
6 protons
6 neutrons
Mass number = 12

9. Average Atomic Mass
The average mass of the element’s isotopes, weighted
according to the abundance of each isotope
This number shows on the periodic table

10. Chapter 9
Lesson 1

11. Radioactivity
Henri Becquerel studied uranium
Marie Curie discovered two new radioactive elements

12. Radioactive
Elements that spontaneously emit radiation
Uranium, radium

13. Nuclear Decay
A process that occurs when an unstable atomic nucleus
changes into another more stable nucleus by emitting
radiation
Alpha decay, beta decay, gamma decay

14. Ions
An atom that is no longer neutral because it has gained
or lost electrons
Positive ions gained a proton
Negative ions gained an electron