TuesdayOctober 23, 2012

(Valence Electrons and Electron Dot

Notation)

Bell Ringer Tuesday, 10-23-12

How many valence electrons does an atom need to have a stable

configuration?

What are the only elements that naturally have a stable electron

configuration?

How do atoms get a stable electron configuration if they do

not naturally have one?

Most atoms have stable electron configurations if they have eight valence electrons (called a stable octet.) What would the following atoms have to do in order to get these eight valence electrons?

2 for H, He8 for all others

the Noble gases

by chemical bonding

sodiumLose 1 Los2 Lose 3

Lose or gain 4,share

Gain 3 Ga Gain 1 nada

magnesium

aluminum

silicon

phosphoru

s

sulfur

chlorine

argonL 1 L 2 L 3 L/G

4G 3 G 2 G 1 nad

a

Bell RingerTuesday, 10-23-12

Write the electron configuration

notation for the following atoms:H, He, Li, C, O, Ne, Na, Cl

Announcements

Assignment Currently Open

Summative or Formative? Date Issued Date Due Date Into

GradeSpeed Final Day

QUIZ 6 S3 10/5 10/5 10/26

QUIZ 7 S4 10/12 10/12 10/26

Pop Quiz – The Periodic Table and the Periodic Law

F4 10/16 10/16

QUIZ 8 S5 10/19 10/19 10/22 11/2

WS – Valence Electrons and

Electron Configuration

F5 10/22 10/24 10/26

WS – Average Atomic Mass F6 10/22 10/24 10/26

The element chlorine has an electron configuration

notation of:

1s2, 2s2, 2p6, 3s2, 3p5

Chlorine has 7 electrons in its highest energy level (3), 2 in the s sub-level and 5 more in the p sub-level.

Chlorine counts all 7 of these valence electrons in its bonding considerations.

Valence Electrons

For main block (s and p) elements, the valence electrons are the

electrons in the outermost s- and p- sublevels.

The inner electrons are in filled energy levels and are held too

tightly by the nucleus to be involved in compound formation.

Valence Electrons

The alkali metals of group 1 have 1 valence electron.

The alkaline earth metals of group 2 have 2 valence electrons.

The elements in the p block (groups 13–18) have a number of valence electrons equal to

their group number minus 10.For example, group 13 has 3 valence

electrons, group 14 has 4, etc.In some cases, both the s- and p- sublevel valence electrons of the p-block elements

are involved in compound formation.In other cases, only the electrons from the p-

sublevel are involved.

Valence Electrons

Number of Highest Energy Level

Electrons (Main Blocks Only)

12 3 4 5 6 7

8

Electron-Dot NotationThus far we have seen three different types

of notation:

isotopic notation

electron configuration notation

orbital notation1s2, 2s2, 2p2

_____ _____ _____ _____ _____ 1s 2s 2px 2py 2pz

Electron-Dot NotationHere’s a fourth type of notation:

Electron-Dot Notation is an electron-configuration notation

in which only the valence electrons of an atom are shown, indicated by dots placed around

the element’s symbol.

Lower energy level, inner - shell electrons are not shown.

Electron-Dot NotationExample: Carbon

Carbon is in group 14 and has four valence electrons.

1s2, 2s2, 2p2

Here’s carbon’s electron-dot notation:

C1. Start with the elemental symbol.2. In your mind, divide the symbol into

quadrants, like a tic-tac-toe grid.3. Beginning in any quadrant put a dot to

indicate a valence electron.4. Continue in a clock-wise direction,

putting one dot in each quadrant before any quadrant gets a second dot.

5. Stop when you have put in the number of dots that correspond to the number of valence electrons that element has.

¢

¢¢

¢

Electron-Dot NotationExample: Fluorine

Fluorine is in group 17 and has seven valence electrons.

1s2, 2s2, 2p5

Here’s fluorine’s electron-dot notation:

F1. Start with the elemental symbol.2. In your mind, divide the symbol into

quadrants, like a tic-tac-toe grid.3. Beginning in any quadrant put a dot to

indicate a valence electron.4. Continue in a clock-wise direction,

putting one dot in each quadrant before any quadrant gets a second dot.

5. Stop when you have put in the number of dots that correspond to the number of valence electrons that element has.

¢

¢¢

¢

¢¢

¢

Electron-Dot Notation

WorksheetElectron Dot Notation