1. 3-3 Modern Atomic Theory By Ms. Pacheco

2. Parts of the Atom NAMECHARGEMASSLOCATION Proton Neutron Electron

3. Parts of the Atom NAMECHARGEMASSLOCATION Proton+1 Neutron Electron

4. Parts of the Atom NAMECHARGEMASSLOCATION Proton+1 Neutron0 Electron

5. Parts of the Atom NAMECHARGEMASSLOCATION Proton+1 Neutron0 Electron

6. Parts of the Atom NAMECHARGEMASSLOCATION Proton+11 amu Neutron0 Electron

7. Parts of the Atom NAMECHARGEMASSLOCATION Proton+11 amu Neutron01 amu* Electron

8. Parts of the Atom NAMECHARGEMASSLOCATION Proton+11 amu Neutron01 amu* Electron0

9. Parts of the Atom NAMECHARGEMASSLOCATION Proton+11 amuNucleus Neutron01 amu* Electron0

10. Parts of the Atom NAMECHARGEMASSLOCATION Proton+11 amuNucleus Neutron01 amu*Nucleus Electron0

11. Parts of the Atom NAMECHARGEMASSLOCATION Proton+11 amuNucleus Neutron01 amu*Nucleus Electron0Electron cloud

12. * Neutrons are slightly larger than protons ** Electrons are so small that their mass is said to be negligible

13. Henry Moseley A British scientist, he is a student of Rutherford In 1913, he makes one of the most important discoveries in chemistry. He found out that an atom’s identity comes from its # of protons (atomic number). Moseley was 26 at the time! 1915: Sadly, Moseley is killed in battle in Turkey during WWI.

14. Said Millikan of Moseley… “…Had the European War had no other result than the snuffing out of this young life, that alone would make it one of the most hideous and most irreparable crimes in history."

15. Henry Moseley in his lab…

16. From Moseley’s ideas, we now know… That since an atom has a neutral charge, then the number of protons must equal the number of electrons. That an atom that loses or gains electrons has a charge and is known as an ion.

17. How to find the charge of an ion… Charge = # P - #E A magnesium ion has 12 protons and 10 electrons. What is its charge? Charge = # P - #E = 12-10 = +2 +2 Mg +2

18. Isotopes… Are atoms that have the same number of protons, but a different number of neutrons.

19. Mass number… Is the sum of an isotopes protons plus neutrons. Is sometimes written at the end of the atom’s name. Ex: carbon-14

20. carbon-12 v’s carbon-14 Both are carbon, so both have 6 protons Their mass numbers are 12 and 14. Due to subtraction, carbon-12 has 6 neutrons and carbon-14 has 8.

21. Atomic Mass… Is the average mass of an element’s atoms as they appear in nature. The atomic masses of all elements are based on the atomic mass of the carbon-12 atom.

22. Chlorine’s Isotopes Chlorine-35 75.53% Chlorine-37 24.47% Therefore, the average mass (atomic mass) of chlorine is 35.45.