1. The Modern Atomic Model

2. The Modern Model Nucleus contains protons and neutrons
Cloudlike region surrounding nucleus contains moving electrons.

3. Particle Charges The number of protons equals the number of electrons.
Neutrons do not affect the charge of the atom.

4. Particle Masses
A Proton and a Neutron have about the same mass (1 amu).
Electrons mass are around 2,000 times less than protons and neutrons.
Protons and Neutrons contribute to most of the atom’s mass.

5. Scale and Size of Atomes
Video

6. Atomic Number
Every atom of an element will always have the same number of protons
Carbon will always have 6 protons, oxygen will always have 8 protons, and iron will always have 26 protons.
The atomic number identifies an element, and is unique to that element and that element only!
Periodic Table

7. Isotopes
Even though atoms will always have the same number of protons, this does not mean that they will always have the same number of neutrons.
Isotopes are when atoms have the same number of protons but a different number of neutrons.

8. Mass Number To find the mass number of an isotope:
(Protons+Neutrons)
Most common isotope is Carbon-12
(6 Protons+6Neutrons)
All carbon atoms will react the same even if they have different mass numbers.
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