1. Do the pre-assessment on a separate sheet of paper.
Structure of Atoms
Do the pre-assessment on a separate sheet of paper.

3. Atom: the smallest unit of matter that retains the identity of an element

4. Atoms 2 regions:
1) Nucleus: center of the atom- contains most the mass
2) Electron shells-region surrounding nucleus-contains most the space of atom
Nucleus
Electron
shells

5. 3 subatomic particles 1) Protons: + charged particles
2) Neutrons: un-charged particles
3) Electrons: - charged particles
In nucleus
In electron shells

6. Atomic Anatomy Proton p+ 1 amu + nucleus neutron n0 Electron e-
What they look like
The guts of an atom
“Subatomic Particles”
# e- = # p+
(for neutral atoms)
Particle (symbol)
Mass
Charge
Location
Proton p+
1 amu +
nucleus
neutron n0
Electron e-
amu -
Electron shells + e- + e-
Nucleus

7. O Name Atomic #: # of protons And same # of electrons Symbol:8 O
Oxygen
15.999
Symbol:
1st letter always capital
2nd letter lowercase
Name
Average Atomic Mass:
# of p+ + # n0
# n0 = mass – atomic #
(Hint: round mass)

8. Practice finding # e-, p+ and n0
Element
Protons
Electrons
Neutrons 7 N
Nitrogen
14.01
14-7 = 7 7 7 15 P
Phosphorus
30.97
31-15 = 16 15 15 11 Na
Sodium
22.99
23-11 = 12 11 11

9. So how do we draw the atoms?
Ex: Li- Three protons (atomic number.) 3 Li
Lithium
6.941 P+ P+ P+

10. Four neutrons. (mass – atomic number.)3 Li
Lithium
6.941 o n0 o o n0 P+ n0 P+ o P+ n0

11. Three electrons, In two electron shells.3 Li
Lithium
6.941 e- e- o n0 o o n0 P+ n0 e- P+ P+ n0

12. Shell #
# of e- 1 2
Go in as a pair 8
1 in each of 4 corners then pair up 3
8 (sort of-more to come) 4

13. Na To check your understanding, draw an atom of Sodium (Na). 11 Sodium
22.990

14. Na 11 p+ 12 n0 Bohr Model of a sodium atom 11 Sodium 22.990 e- e- e-
For bigger atoms, it is easier to write the number of protons and neutrons in the nucleus, than draw each of them out.
You should always draw each electron. e- e-
11 p+ 12 n0 11 Na
Sodium
22.990 e- e- e- e- e- e- e- e- e-

16. What do I need to Know? You must be able to draw elements 1-36
Everyone should know the name/chemical symbol for elements 1-36 plus gold, sliver, mercury, iodine, and lead

17. Do Now: 10/8
Compare the relative size, location and mass of the three sub atomic particles.
Draw a Bohr model for an atom of calcium.

18. More Practice 6 5 5 20 20 20 2 2 2 B Ca He 11-5 = 40-20 = 4-2 =
Element
Protons
Electrons
Neutrons 5 B
Boron
10.81
11-5 = 6 5 5 20 Ca
Calcium
40.08
40-20 = 20 20 20 2 He
Helium
4.00
4-2 = 2 2 2