1. Structure of the Atom (Section 4.2)

2. Subatomic Particles Light up your old tv screen
When the beam sweeps across your screen it lights up spots
There are three beams, one for each primary color of light
Red
Green
Blue
Particles in the beams are subatomic particles

3. Properties of Subatomic Particles
Protons, electrons, and neutrons are subatomic particles
Protons - a positively charged subatomic particle that is found in the nucleus of an atom
Charge is +1, Mass = 1
Electrons - a negatively charged subatomic particle that is found in the space outside the nucleus
Charge is -1, mass = 1/2000
Greek word means amber
Neutrons - a neutral subatomic particle that is found in the nucleus of an atom, no charge
Mass is almost exactly equal to that of a proton (mass = 1)

4. Comparing Subatomic Particles
Protons, electrons, and neutrons can be distinguished by mass, charge, and location in an atom
Protons and neutrons have almost the same mass
Protons have a positive charge
Neutrons have no charge
Both are found in the nucleus

5. Comparing Subatomic Particles
Electrons have a mass about 2000 times smaller than that of a proton
But its charge is equal in size to and opposite of the charge of a proton
Found in the space outside the nucleus

6. Atomic Number
The atomic number of an element equals the number of protons in an atom of that element
Atoms of different elements have different numbers of protons
Can be used to refer to different elements
Atomic number is also the number of electrons for an atom because the charges are balanced

7. Mass Number
Mass number - The sum of the protons and neutrons in the nucleus of an atom
Mass # = # protons + # neutrons
To find the number of neutrons in an atom subtract the atomic number from the mass number
# neutrons = mass # - Atomic #

8. Isotopes
Isotopes - atoms of the same element that have different numbers of neutrons and therefore different mass numbers
Isotopes of an element have the same atomic number but different mass numbers because they have different numbers of neutrons
Every atom of oxygen has 8 protons but some atoms have 8 or 9 or even 10 neutrons
Atoms with 8 have a mass number of 16
Atoms with 9 have a mass number of 17
Atoms with 10 have a mass number of 18

9. Isotopes
With most elements it is hard to notice any differences in the physical or chemical properties between the isotopes
Hydrogen-1 only has 1 proton and no neutrons
Hydrogen-2 has 1 proton and 1 neutron which doubles its mass, water that contains hydrogen-2 is called heavy water