Electrons in Atoms. Bohr’s Model Electrons move like planets around the sun. In circular orbits at different levels. Amounts of energy separate.

Electrons in AtomsElectrons in Atoms

Bohr’s ModelBohr’s Model Electrons move like planets around the Electrons move like planets around the

sun.sun. In circular orbits at different levels.In circular orbits at different levels. Amounts of energy separate one level Amounts of energy separate one level

from another.from another.

The Bohr Model of the AtomThe Bohr Model of the Atom

A.A. Electrons of hydrogen circle the Electrons of hydrogen circle the nucleus in orbitsnucleus in orbits

1. 1. orbitsorbits have a fixed amount of energy have a fixed amount of energy

in the ground statein the ground state

2. 2. orbitsorbits are a fixed distance from the are a fixed distance from the

nucleusnucleus

3.3. orbitsorbits furthest from the nucleus have furthest from the nucleus have

the greatest energythe greatest energy

4. Electrons in the 4. Electrons in the ground stateground state can absorb can absorb quanta of energy – become quanta of energy – become excitedexcited- and - and move to a higher orbitmove to a higher orbit

5. Electrons emit 5. Electrons emit quantaquanta of energy when of energy when

they return to the ground statethey return to the ground state

6. Model applies only to hydrogen atoms 6. Model applies only to hydrogen atoms

Niels Bohr Niels Bohr (1885 – 1962) Bohr Model of the Atom(1885 – 1962) Bohr Model of the Atom

Bohr’s ModelBohr’s Model

Nucleus

Electron

Orbit

Energy Levels

Bohr’s ModelBohr’s ModelIn

crea

sing

ene

rgy

Nucleus

First

Second

Third

Fourth

Fifth

} Further away from Further away from

the nucleus the nucleus means more means more energy.energy.

There is no “in There is no “in between” energybetween” energy

Energy LevelsEnergy Levels

BohrBohr

Make a model of Bohr’s Hydrogen. Bohr Make a model of Bohr’s Hydrogen. Bohr was only correct about Hydrogen.was only correct about Hydrogen.

Draw a nucleus Draw a nucleus Then draw the electron.Then draw the electron.

Changing the energyChanging the energy Let’s look at a hydrogen atomLet’s look at a hydrogen atom

Changing the energy Heat or electricity or light can move the Heat or electricity or light can move the

electron up energy levelselectron up energy levels

Changing the energy As the electron falls back to ground state it As the electron falls back to ground state it

gives the energy back as lightgives the energy back as light

May fall down in stepsMay fall down in steps Each with a different energyEach with a different energy

Changing the energy

II.Heisenberg Uncertainty II.Heisenberg Uncertainty PrinciplePrinciple

It is impossible to know exactly the position It is impossible to know exactly the position and velocity of a particle at the same time.and velocity of a particle at the same time.

The better we know one, the less we know The better we know one, the less we know the other.the other.

The act of measuring changes the The act of measuring changes the properties.properties.

Look at the fanLook at the fan

Covalent clipCovalent clip

I.The Covalent BondI.The Covalent Bond A. Why do atoms form bonds?A. Why do atoms form bonds?

1. To get 8 valence shell electrons 1. To get 8 valence shell electrons

(noble gas configuration) (noble gas configuration)

2. more stable configuration - 2. more stable configuration -

less potential energyless potential energy

B. Definition of Covalent BondB. Definition of Covalent Bond

1. bond resulting from sharing electrons1. bond resulting from sharing electrons

2. share electrons by overlapping of 2. share electrons by overlapping of

orbitalsorbitals

I.The Covalent BondI.The Covalent Bond A. Why do atoms form bonds?A. Why do atoms form bonds?

1. To get 8 valence shell electrons 1. To get 8 valence shell electrons

(noble gas configuration) (noble gas configuration)

2. more stable configuration - 2. more stable configuration -

less potential energyless potential energy

B. Definition of Covalent BondB. Definition of Covalent Bond

1. bond resulting from sharing electrons1. bond resulting from sharing electrons

2. share electrons by overlapping of 2. share electrons by overlapping of

orbitalsorbitals

Covalent Bonds – Sharing of ElectronsCovalent Bonds – Sharing of Electrons

The Lewis dot structure for Oxygen

OOxygen is in group VIA so it has 6 valence electrons

The Lewis dot structure for Chlorine

Clchlorine is in group VIIA so it has 7 valence electrons

The Lewis dot structure for calcium

Cacalcium is in group IIA so it has 2 valence electrons

Making calcium chloride

+Ca Cl Cl

Ca( Cl )2

Lewis dot structure of a compound

NH3

N

H

H

H

Lewis dot structure of a compound

NH3

1) How many valence electrons does N have?N is in group VA so it has 5 valence electrons

2) How many valence electrons does H have? H is in group IA so each H has one valence electron

3) How many valence electrons does Neon have.

Water - HWater - H22OO

H

O

Each hydrogen has 1 valence Each hydrogen has 1 valence electronelectron

Each hydrogen wants 1 moreEach hydrogen wants 1 more

The oxygen has 6 valence The oxygen has 6 valence electronselectrons

The oxygen wants 2 moreThe oxygen wants 2 more

They share to make each other They share to make each other happyhappy

WaterWater Put the pieces togetherPut the pieces together The first hydrogen is happyThe first hydrogen is happy The oxygen still wants one moreThe oxygen still wants one more

H O

WaterWater

The second hydrogen attachesThe second hydrogen attaches Every atom has full energy levelsEvery atom has full energy levels

H OH

Lewis structure Lewis structure

1. PH1. PH33

2. H2. H22SS

3. HCl3. HCl

4. CCl4. CCl44

5. SiH5. SiH44

Lesson 3Lesson 3

Lewis structure Lewis structure

Use molecular model kit to buildUse molecular model kit to build 1. PH1. PH33 2. H2. H22SS

3. HCl3. HCl 4. CCl4. CCl44 5. SiH5. SiH44 6. CH6. CH44

7. ClF3 8. PCl5 9. SO2 10. N2O5

1.ClF3

2.PCl5

3.SO2

4.N2O5

Isomers-Isomers-Build the moleculeBuild the molecule

On the right using On the right using springs for double springs for double bonds.bonds.

3. 3. diatomic moleculesdiatomic molecules (contain two atoms) (contain two atoms)

a. periodic table (1,1-7--->group 17) a. periodic table (1,1-7--->group 17)

elements that form diatomic molecules elements that form diatomic molecules

HH22 N N22 O O22 F F22 Cl Cl22 Br Br22

b. compounds can also be b. compounds can also be diatomicdiatomic

HCl CO NO HF HI HBrHCl CO NO HF HI HBr

C. Examples and DiagramsC. Examples and Diagrams

HH22 F F22 HF HF

Make a drawingMake a drawingD. What is a molecule?D. What is a molecule?

1. two or more atoms bonded covalently1. two or more atoms bonded covalently

2. examples- Make a drawing2. examples- Make a drawing

(usually two or more nonmetals) (usually two or more nonmetals)

HH22O NHO NH33 CH CH44 N N22OO55 HCl HCl

CC66HH1212OO66