1. When Atoms Change: Isotope Notes

2. What we KNOW… Atoms on the periodic table are neutral.
Atoms are neutral because they have the same number of protons as electrons.
protons  have a positive charge.
neutrons  have no charge.
electrons have a negative charge.

3. What we Also need to KNOW…
The identity of an atom is determined ONLY by the number of protons.
For example… If I tell you there is an atom with 3 protons… you know it’s a Lithium atom.
What about 8 protons, 13 protons, 79 protons???

4. What happens if the number of neutrons change???
If an atom gains Neutrons…
1. The mass increases by 1 for every neutron added.
2. The charge remains neutral. (Neutrons don’t have a charge.)
3. The number of protons and electrons stay the same.
If an atom loses Neutrons…
The mass decreases by 1 for every neutron taken away.
The charge remains neutral. (Neutrons don’t have a charge.)
The number of protons and electrons stay the same.

5. The atom is now called an ISOTOPE! When atoms gain or lose neutrons!

6. ISOTOPE EXAMPLE Hydrogen Atom
                                              
                                                                  
Hydrogen Atom
Has a mass of 1 and an atomic number of 1
Hydrogen Isotope
Has a mass of 2 and an atomic number of 1

7. ISOTOPE NOTATION
We communicate that we have an isotope by using the Atomic Symbol of the isotope followed by the “NEW” mass number.
Ex: An Isotope of Lithium is:
Li - 7
Atomic
Symbol
Mass Number

8. Isotope INVENTORY
Completing a particle inventory for an Isotope is almost the same as the neutral atom EXCEPT we USE THE “NEW” MASS NUMBER to calculate neutrons.
Ex: Li-6
3p+ (since it’s Lithium!!!)
3e- (since they are still equal to p+) 3n
(6-3 = 3)

9. Isotope Practice Ca atom has a mass of 40. The isotopes for Ca are:
Ca-42, Ca-43,Ca-44, Ca-46, & Ca-48.
1.) How many neutrons are in a Ca atom and each of its isotopes?
2.) What are the differences and similarities between the Ca atom and its isotopes?