Chapter 1Chapter 1Activity 7:Activity 7:

How Electrons How Electrons Determine Chemical Determine Chemical

BehaviorBehavior

Bohr Model—shows the electrons in various energy levels

How many electrons can fit into each energy level??????

Max # e- = 2n2 where n= energy level

Ex. If n=1 (1st energy level), then 2(1)2=Ex. If n=2 (2nd energy level), then 2(2)2=Ex. If n=3 (3rd energy level), then 2(3)2=

Valence ElectronsValence ElectronsValence electrons

◦Electrons in the outermost energy level of an atom

Valence ElectronsValence ElectronsThe Group Number tells us the # of valence electrons.

Valence ElectronsValence ElectronsThe Group Number tells us the # of valence electrons.

Valence e-

increases across a period

Valence e- stays

the same

down a group

Valence ElectronsValence ElectronsHow many valence electrons does

◦a Fluorine atom have?◦a Magnesium atom have?◦an element in the noble gas family have?◦

Things You Need to Now KnowThings You Need to Now Know

On the periodic table:

◦The COLUMN or GROUP or FAMILY equals the # of valence electrons (for columns 1,2, 13-18)

◦The ROW or PERIOD equals the energy level

Bohr ModelsBohr Models

Rutherford focused on describing the nucleus

Bohr focused on describing the location of the electrons

Bohr model (planetary model): -shows electrons moving in orbits (energy levels) around the positive nucleus of the atom.

Bohr model for HydrogenBohr model for Hydrogen

1H

1

                                                                                                                  

                              

Hydrogen is in period 1 = 1st energy level

Hydrogen is the first box in period 1 = 1 electron

Energy level 1

# of Electrons in that Energy level

Bohr model for LithiumBohr model for Lithium

3Li

2 1                                             

                                                                                                     

Lithium is in period 2 = 2nd energy level

Lithium is the first box in period 2 = 1 electron

Energy level 1

# of Electrons in 1st Energy level

Energy level 2

# of Electrons in 2nd Energy level

Using What You Now KnowUsing What You Now KnowDuet Rule: In forming compounds,

atoms tend to gain or lose electrons in order to have two electrons in their first energy level.

Octet Rule: In forming compounds, atoms tend to gain or lose electrons in order to have eight electrons in their outer energy level.

StabilityStability

9F

2 7

                                            

                                                                                                     

Atoms will lose or gain electrons to have a filled outer energy level (duet rule or octet rule).

This fluorine atom has only 7 valence electrons

The octet rule isn’t satisfied

Stability Stability A fluorine atom will try and gain an

electron (7e- + 1e- = 8e-).

With 8e-s, it is now an ANION (-1) with 8 valence electrons

The anion now obeysthe octet rule.

-1

9F

2 8

-1

StabilityStability

11Na

2 8 1

This sodium atom has 1 valence electron.

The octet rule isn’t satisfied.

StabilityStability

11Na

2 8

If the sodium atom loses it’s valence electron, it will now have 8 valence electrons.

The octet rule is satisfied.

+1

Why Atoms ReactWhy Atoms ReactSome atoms want to lose valence electrons more

than others -nonmetals want to keep their valence electrons

-metals want to lose their valence electrons

Why Atoms ReactWhy Atoms React• nonmetals want to keep their valence electrons

• metals want to lose their valence electrons