1. Topic: Atomic Concepts
Aim: How are electrons arranged in an atom?
Do Now:
Take out HW
Wkst – Element Symbols – pick 10 from top and 10 from bottom.
Wkst – chart – fill in the information for the elements that do NOT have charges written next to them.
HW:

2. What about electrons? Atomic # = ____ & ____ (for a neutral atom)
# of neutrons = ____
The protons & neutrons are located ___
How are electrons arranged in the electron cloud?

3. Arrangement of Electrons
Principal Energy Levels (PELs)
Show distance from nucleus
Up to 7 PELs
Electrons in different shells have different energies.
Low PEL# = close to nucleus = low energy
High PEL# = far from nucleus = high energy

4. Atom with PELs n = 1, low energy n = 2, more energy
n = 3, more energy than 2
Nucleus containing p & n

5. How many e- can each PEL hold?
PEL (n)
Max # of e- it can hold (2n2) 1 2 8 3 18 4 32

6. Electron Configuration
How e- fill the PELs – how many e- are in each PEL
Always start with PEL #1 (closest to the nucleus) & work your way out
Once PEL #1 is full, the rest of the e- start to fill in PEL #2 till it’s full
This info is on the PERIODIC TABLE!

7. Example Electron Configuration
The 2 means there are 2 electrons in PEL #1. (PEL #1 is full.)
The 4 means there are 4 electrons in PEL #2.

8. More Examples Magnesium & Zinc – for each… Atomic # # of e- e- config
# of PELs occupied

9. Valence Electrons OUTERMOST e-
These e- participate in chemical rxns with other atoms
Give an element its chemical properties
Last # of e- configuration
How many valence e- does magnesium have? Zinc?
Valence e-

10. X • • • • • • • • Lewis Dot Structures
Shows VALENCE e- as DOTS around ATOMIC SYMBOL
Symbol will have a MAXIMUM of 8 dots! Why? • • X • • • • • •

11. Examples Draw the Lewis structures for the following elements: Helium
Sulfur
Boron
Nitrogen
Neon