1. Atomic Structure The atom as we understand it today

2. Atomic Structure The atom consists of 3 subatomic particles? Do you know what they are? Proton ElectronNeutron

3. The following notation is used: A X Z A = Mass Number Z = Atomic Number

4. Atomic Structure Atomic Number (Z) – this is unique to each atom. The atomic number is equal to the number of protons. Mass Number (A) – this is the total mass of each atom. Remember, each P and N has a mass of about 1amu. amu = 1/12 the mass of a C-12 atom Therefore, the mass number = #P + #N

5. Atomic Structure The atom written as 36 17 Cl can also be expressed as Cl-36. The 17 is understood, because we are referring to the chlorine atom. The 36 refers to the Mass Number.

6. Atomic Structure Make the following grid in your notes: ElementAtomic #Mass ##P#N#e C-12 F-14 N-14 Na-25 Li-8

7. Atomic Structure Make the following grid in your notes: Element 119 50 Sn 238 92 U Protons 17 Neutrons 85 Electrons 92 Atomic Number 8292 Mass Number 36235

8. Atomic Structure Can we have both U-235 and U-238? Yes! They are referred to as Isotopes. Isotopes are atoms of the same element ( they have the same number of P) but they contain a different number of Neutrons. ( This is what changes the mass number)

9. Atomic Structure Now what do we do when we are given: 60 27 Co 2+ We now have: P: 27 N:33 e-: 25 (We have two fewer electrons than P)

10. Atomic Structure ***WARNING*** Never change the number of protons when a charge is present, ALWAYS change the number of e-. A positive charge (More P than e-) A negative charge (More e- than P)

11. Atomic Structure Make the following grid in your notes: Element 25 12 Mg 2+126 51 Sb 3+ Protons 17 Neutrons 85 Electrons 182610 Atomic Number 285113 Mass Number 3627