Electron Arrangement: electrons (e) are found in energy levels outside of the nucleus. Energy level(s) = Orbit(s) or Shell(s) where e are found. (a.k.a.

Electron Arrangement:

• electrons (e) are found in energy levels outside of the nucleus.

• Energy level(s) = Orbit(s) or Shell(s) where e are found.

(a.k.a. “Principal Energy Level(s)”)

• Period = Horizontal (left right) row in the periodic table.

• Period # = the # of occupied energy levels (E.L.)

• Q: How many periods are there on the periodic table???

There are a total of 7 possible E.L.

• 1st Energy level (1st E.L.) = closest to nucleus.

• has LEAST energy of all E.L.

• 7th E.L. has MOST energy of all E.L.

• e only occupy the orbits of lowest E.L. first.

• Eg. e fill up 1st E.L. fill up 2nd E.L. . . . fill up 7th E.L.

Formula for # of e allowed in each E.L.:

• n = E.L.• (Eg. n = 6 6th E.L.)

• ** 2n2 = # of e that can occupy E.L. “n”. **

Q.1. How many e can occupy E.L. 1?

Q.2. Fill in the following Table. (show work on the side)

Energy level (n) max. # of electrons allowed(2n2)

1 22

3

4

5

6

7

Octet Rule

• Octet Rule – The valence E.L. can never hold more than 8 e-.

– Valence E.L. = outermost shell

– Valence electrons = electrons on the valence (outermost) shell.

Octet Rule (cont’d)

• All Elements WANT to have a FULL valence energy level (shell)

– Full valence shell = 8 e- (or 2 e- if 1st E.L.)

• H and He only want 2 valence electrons

• Why???

Octet Rule (Cont’d)• Eg. draw the Bohr model of potassium-38 (38K)

Q.1) How many valence e- does K have?

Q.2) How many valence e- does K want?

Q.3) What is the easiest (least energy) way for K to obtain this???

Energy Levels

Electron Configuration

• Electron Configuration: The # of electrons according to the shell they’re in.

– Write out the # of e- according to the shell they’re in.

Eg. H Li Electron Config. = Electron Config. =

Symbol Electron Config. Symbol Electron Config.

1 11

2 12

3 13

4 14

5 15

6 16

7 17

8 18

9 19

10 20

Ground State vs. Excited State

• “Ground State” and “Excited State”

– refers to the state of the atom based on location of electrons.

Ground State

• Ground State:

– Electrons occupy LOWEST E.L. (Energy Levels).

1. LOW Energy

2. STABLE Why???

** P.T. shows ground state only!!! **

Excited State

• Excited State:

– Electron “jumps” to HIGHER energy level (temporarily)

Excited State

• “jump up” ABSORBS energy

“sugar high”

• “fall down” RELEASES energy (as LIGHT!)

“sugar low”

• UNSTABLE

• HIGH Energy

• Exciting an electron

Excited State

• Drawing of atom in the excited state:

Excited State

• Flame Test– Formed by the heating of metal ions, using a

flame.

• Demo – Flame Tests (Cu, Li, K, Na, Sr)

Q.) Why does the flame cause this effect?

Excited State

• Spectral Lines: “the DNA code of elements”

– Formed by Gases (must use electricity)

• Spectral lines

***Demo – Spectral lines

***must use 3-D glasses.

Excited State – Spectral LinesQ.: Based on the line spectra, which of the

following elements are contained in the unknown sample?

Excited vs. Ground State

• Label each of the following as being in the ground state or excited state:

*(see if you can convert excited ground)

A.) 2-8-1

B.) 1-8

C.) 2-8-7-1

D.) 2-7-5

E.) 2-8-18-5

Electron Dot Diagram

• Electron Dot Diagram:

– Illustrates the element symbol surrounded by the valence electrons.

• Eg.1. Draw the Electron Dot Diagram:

H C Ca

Electron-dot Diagrams (cont’d)

Ne B N Ba

S F Hg Cl

Groups

• Groups:• Vertical (up and down) columns on

the P.T.

• Q. What do elements in the same group have in common???