1. Ch. 3 Atoms
3.3 Counting Atoms

2. Atomic Number (Z) number of protons
All atoms of the same element have the same atomic number
located above the symbol in the periodic table
order of the elements in the periodic table

3. Isotopes atoms of the same element with different numbers of neutrons
most elements exist as a mixture of isotopes
What do the Carbon isotopes below have in common? What is different about them?

4. Mass Number sum of particles in nucleus A = #p + #n
Hydrogen isotopes have special names:
protium
deuterium
tritium
What do the
prefixes
in their names
come from?

5. Designating Isotopes Hyphen notation: Nuclear Symbol notation:
Name - mass number
ex. Carbon – 13
Nuclear Symbol notation:

6. Examples 7 protons, 8 neutrons Nitrogen-15 17 electrons, 19 neutrons
Chlorine- 36

7. Examples
3. Z=5, 6 neutrons
Boron- 11
4. A=75, 42 neutrons
Arsenic- 75

8. Examples Carbon- 13 Xenon-131 Sodium-24 Oxygen- 15 #p #n #e Z A

9. Examples #p #n #e Z A