Unit 3Unit 3

Valence Electrons and IonsValence Electrons and Ions

Subatomic ParticlesSubatomic Particles

In an atom Protons and neutrons are In an atom Protons and neutrons are clumped together in a very small clumped together in a very small dense nucleusdense nucleus

The Electrons are found outside of The Electrons are found outside of the nucleus in various electron cloudsthe nucleus in various electron clouds

Principle Energy LevelsPrinciple Energy Levels

The electron clouds are found at The electron clouds are found at specific distances from the nucleus specific distances from the nucleus called called Principle Energy LevelsPrinciple Energy Levels

Lowest energy levels are closest to the Lowest energy levels are closest to the nucleusnucleus

Highest energy levels are farthest Highest energy levels are farthest from the nucleusfrom the nucleus

Fill from Lower Fill from Lower Higher energy levels Higher energy levels

Energy Level ‘Clouds’Energy Level ‘Clouds’

phycomp.technion.ac.il/~phr76ja/lecture1.html hoku.as.utexas.edu/.../a309f04/lect1cos.html

BohrBohr

The Bohr model is used to show The Bohr model is used to show electron placements in the energy electron placements in the energy levels.levels.

Elements in the same row of the Elements in the same row of the periodic table have the same number periodic table have the same number of occupied energy levelsof occupied energy levels

Energy LevelsEnergy Levels

First energy level- max First energy level- max 2 electrons2 electrons

Second energy level- max Second energy level- max 8 electrons8 electrons

Third energy level- max Third energy level- max 8 electrons8 electrons

Fourth energy level- max Fourth energy level- max 18 electrons18 electrons

Valence ElectronsValence Electrons

The electrons that occupy the The electrons that occupy the highest energy level (or the outer highest energy level (or the outer shell) are called shell) are called Valence ElectronsValence Electrons

Valence electrons are important Valence electrons are important because they are the electrons because they are the electrons involved in chemical reactionsinvolved in chemical reactions

This means that the number of This means that the number of valence electrons determines an valence electrons determines an element’s chemical propertieselement’s chemical properties

Valence ElectronsValence Electrons

Elements in the same column of the Elements in the same column of the Periodic Table have the same Periodic Table have the same number of valence electrons and number of valence electrons and have similar chemical properties.have similar chemical properties.

IonsIons

When elements undergo chemical When elements undergo chemical reactions they either share or reactions they either share or exchange electrons with other exchange electrons with other elements to fill their outer shells.elements to fill their outer shells.

Atoms that have either lost or gained Atoms that have either lost or gained electrons are called ions.electrons are called ions.

Unlike neutral atoms, ions have a net Unlike neutral atoms, ions have a net charge.charge.

Ion ChargesIon Charges

The number of electrons that it has lost or The number of electrons that it has lost or gained determines an ion’s chargegained determines an ion’s charge

Ions that Ions that GAINGAIN electrons have a electrons have a NEGATIVENEGATIVE charge and are called charge and are called anionsanions..

Ions that Ions that LOSELOSE electrons have a electrons have a POSITIVEPOSITIVE Charge and are called Charge and are called cations.cations.

Lithium Loses an ElectronLithium Loses an Electron

Li Li Li Li+1+1 + 1 e- + 1 e-

LiLi LiLi+1+1

Fluorine gains an electronFluorine gains an electron

F + 1 e- F + 1 e- F F-1-1

FF FF-1-1

Lithium FluorideLithium Fluoride

F + 1 e- F + 1 e- F F-1-1

Li Li Li Li+1+1 + 1 e- + 1 e-

Li + F Li + F LiF LiF

HClHCl

Draw Bohr Models for Hydrogen and Draw Bohr Models for Hydrogen and Chlorine and then show how they Chlorine and then show how they combine.combine.

Cl + 1 e- Cl + 1 e- Cl Cl-1-1

H H H H+1+1 + 1 e- + 1 e-

H + Cl H + Cl HCl HCl

Ion DrawingsIon Drawings

Draw Bohr models for the following Draw Bohr models for the following elements:elements:– OxygenOxygen– Sodium Sodium – MagnesiumMagnesium– BromineBromine

Ion DrawingsIon Drawings

In your lab groups draw Bohr models In your lab groups draw Bohr models for the following elements:for the following elements:– Oxygen (2)Oxygen (2)– Hydrogen (2)Hydrogen (2)– Sodium (1)Sodium (1)– Chlorine (1)Chlorine (1)– Magnesium (1)Magnesium (1)– Calcium (1)Calcium (1)– Bromine (2)Bromine (2)

Combine IonsCombine Ions

Cut out the circles and combine the Cut out the circles and combine the Ions to make the following Ions to make the following compounds. Draw arrows to show the compounds. Draw arrows to show the movement of the electronsmovement of the electrons– HH22O O WaterWater

– NaClNaCl Sodium ChlorideSodium Chloride

– CaBrCaBr22 Calcium BromideCalcium Bromide

– MgOMgO Magnesium OxideMagnesium Oxide