Unit 3Unit 3Periodic TablePeriodic Table

and Valence electronsand Valence electrons

Valence electronsValence electrons

Valence electrons are electrons Valence electrons are electrons located in the outermost energy located in the outermost energy level.level.

They are located only in the They are located only in the s and p s and p sublevelssublevels

These electrons are involved in These electrons are involved in chemical bonding.chemical bonding.

Electron ConfigurationsElectron Configurations

An element’s electron configuration An element’s electron configuration shows how many valence electrons it shows how many valence electrons it has.has.

Example:Example:

1s1s222s2s222p2p663s3s223p3p664s4s223d3d10104p4p44

Valence electrons = 6

PracticePractice

How many valence electrons do the How many valence electrons do the following elements have?following elements have?

1s1s222s2s222p2p663s3s223p3p664s4s223d3d10104p4p66

1s1s222s2s222p2p663s3s223p3p22

1s1s222s2s22

8 valence electrons

4 Valence Electrons

2 valence electrons

Octet RuleOctet Rule Most elements want to have 8 valence Most elements want to have 8 valence

electrons (exception He)electrons (exception He)

Elements will gain or lose electrons in Elements will gain or lose electrons in their valence shell in order to achieve an their valence shell in order to achieve an octet.octet.– This process forms This process forms IonsIons..

Ions have the same electron Ions have the same electron configuration as their nearest configuration as their nearest noble gasnoble gas..

Positive IonsPositive Ions

Elements with less than 4 valence Elements with less than 4 valence electrons lose their outermost “s” electrons lose their outermost “s” and “p” sublevel electrons and “p” sublevel electrons

ExampleExample

Be: 1sBe: 1s222s2s2 2 has 2 valence electrons has 2 valence electrons

BeBe2+2+: 1s: 1s22 notice the ion has the samenotice the ion has the same

configuration as Heconfiguration as He– They always form positive ions.They always form positive ions.

Negative IonsNegative Ions

Elements with more than 4 valence Elements with more than 4 valence electrons gain electrons in their electrons gain electrons in their outermost “p” subleveloutermost “p” sublevel

ExampleExample

O: 1sO: 1s222s2s222p2p44 has 6 valence electronshas 6 valence electrons

OO2-2-: 1s: 1s222s2s222p2p66 now has 8 valencenow has 8 valence

electrons just like Neelectrons just like Ne– They always form negative ions.They always form negative ions.

Ion Formation SummaryIon Formation Summary Atoms gain or lose electrons to Atoms gain or lose electrons to

become more stable.become more stable.– They achieve the same electron They achieve the same electron

configuration as the Noble Gases.configuration as the Noble Gases.

Shorthand ConfigurationShorthand Configuration

S 16e-

Valence Electrons

Core Electrons

S 16e- [Ne] 3s2 3p4

1s2 2s2 2p6 3s2 3p4

Noble Gas Shorthand Electron Noble Gas Shorthand Electron ConfigurationsConfigurations

Longhand ConfigurationLonghand Configuration

Noble Gas Shorthand Noble Gas Shorthand ConfigurationConfiguration

Shorthand ConfigurationShorthand Configuration– Core eCore e--:: Go up one row and over to the Go up one row and over to the

Noble Gas.Noble Gas.

– Valence eValence e--:: On the next row, fill in the On the next row, fill in the # of e# of e-- in each sublevel. in each sublevel.

[Ar] 4s2 3d10 4p2

Noble Gas Shorthand NotationNoble Gas Shorthand Notation Example - Example - GermaniumGermanium

Modern Periodic TableModern Periodic Table

Elements are arranged by increasing Elements are arranged by increasing atomic number.atomic number.– Recall that atomic number gives the Recall that atomic number gives the

number of protons in the nucleus of an number of protons in the nucleus of an atom.atom.

PeriodsPeriods

Horizontal rows on the periodic table Horizontal rows on the periodic table are called periods.are called periods.

Elements in the same period have Elements in the same period have the same number of valence shells.the same number of valence shells.

Elements in the same period share Elements in the same period share no similar chemical properties. no similar chemical properties.

PeriodsPeriods

Groups / FamiliesGroups / Families

Vertical columns on the periodic Vertical columns on the periodic Table are called groups.Table are called groups.

Groups are numbered 1-18Groups are numbered 1-18

Elements in the same group have the Elements in the same group have the same chemical properties because same chemical properties because they have the same number of they have the same number of valence electrons.valence electrons.

Some groups have special names.Some groups have special names.

Groups/FamiliesGroups/Families

Group 1 MetalsGroup 1 Metals

Known as Known as Alkali MetalsAlkali Metals Most active metals on periodic tableMost active metals on periodic table React violently with water, and React violently with water, and

become more active down the groupbecome more active down the group Only have 1 valence electron Only have 1 valence electron

(because they all end in s(because they all end in s11)) They all form ions with a +1 charge.They all form ions with a +1 charge.

Group 2 MetalsGroup 2 Metals Known as Known as Alkaline Earth MetalsAlkaline Earth Metals Also extremely reactive, but not as Also extremely reactive, but not as

much as Alkali Metalsmuch as Alkali Metals Contain 2 valence electrons (they end Contain 2 valence electrons (they end

in sin s22)) They all form ions with a +2 charge.They all form ions with a +2 charge.

Groups 3-12Groups 3-12 These groups are known as These groups are known as

Transition MetalsTransition Metals Not very reactive metalsNot very reactive metals Generally have 2 valence electrons Generally have 2 valence electrons Some of their “d” orbital electrons Some of their “d” orbital electrons

jump around into “p” orbitals so jump around into “p” orbitals so many of these elements have more many of these elements have more than one possible positive charge.than one possible positive charge.

Form colorful ion solutions (bright Form colorful ion solutions (bright vibrant colors)vibrant colors)

Group 17Group 17 Known as Known as HalogensHalogens Extremely reactive nonmetals; reactivity Extremely reactive nonmetals; reactivity

increases up a group (Fluorine the most increases up a group (Fluorine the most active)active)

Have 7 valence electrons (eHave 7 valence electrons (e-- configuration configuration ends in sends in s22pp55))

Most of these elements are toxic in their Most of these elements are toxic in their natural statenatural state

Most are also diatomic in their natural state Most are also diatomic in their natural state (F(F22, Br, Br22, Cl, Cl22, I, I22))

They all form ions with a (-1) charge.They all form ions with a (-1) charge.

Group 18Group 18 Known as Known as Noble gasesNoble gases Unreactive nonmetalsUnreactive nonmetals All have 8 valence electronsAll have 8 valence electrons (e- configuration ends in s(e- configuration ends in s22pp66), ),

except Helium (which has 2 except Helium (which has 2 electrons)electrons)

They do not form ions.They do not form ions.