4.1 Atomic Theory & Bonding4.1 Atomic Theory & Bonding

ATOMATOM:: smallest particle of an element, has a neutral charge. smallest particle of an element, has a neutral charge.PEN = proton(s) + electron(s) + neutron(s)PEN = proton(s) + electron(s) + neutron(s)

ELEMENTELEMENT:: made up of 1 type of atom (eg.oxygen O) made up of 1 type of atom (eg.oxygen O)IONS:IONS: atoms with charges (eg. oxygen is O atoms with charges (eg. oxygen is O2-2-))MOLECULES: MOLECULES: groups of covalently bonded atoms (eg. oxygen oxygen

molecules are Omolecules are O22))

COMPOUNDS:COMPOUNDS: are made up of at least 2 atoms bonded are made up of at least 2 atoms bonded together.together.

Hydrogen and oxygen are atoms/elementsHydrogen and oxygen are atoms/elements HH22O is a compoundO is a compound

Structure of an Atom:Structure of an Atom:

NameName SymbolSymbol ChargChargee

LocationLocation Atomic Atomic MassMass

ProtonProton pp 1+1+ nucleusnucleus 1 AMU1 AMU

NeutronNeutron nn 00 nucleusnucleus 1 AMU1 AMU

ElectronElectron ee 1–1– area surrounding area surrounding the nucleusthe nucleus 1/1836 (0)1/1836 (0)

Numbers to Remember :Numbers to Remember :

Protons Protons = Atomic Number= Atomic Number

NeutronsNeutrons = Mass number – Atomic number (Mass = Mass number – Atomic number (Mass # - proton #).# - proton #).

Neutrons + Protons = Mass #Neutrons + Protons = Mass #

Electrons in an atomElectrons in an atom = atomic number (also = atomic number (also proton #)proton #)

Electrons in an ionElectrons in an ion = atomic number – ion charge = atomic number – ion charge

Families of the Periodic Table:Families of the Periodic Table:

Columns of elements are called Columns of elements are called groupsgroups, or , or familiesfamilies All elements in a family have…All elements in a family have…

similar propertiessimilar properties bond with other elements in similar waysbond with other elements in similar ways have the same number of valence electronshave the same number of valence electrons

Family names (on the periodic table!):Family names (on the periodic table!): Group 1 = alkali metals (1Group 1 = alkali metals (1++, highly reactive), highly reactive) Group 2 = alkaline earth metals (2Group 2 = alkaline earth metals (2++, reactive), reactive) Group 17 = the halogens (1Group 17 = the halogens (1--, very reactive), very reactive) Group 18 = noble gases (0, unreactive)Group 18 = noble gases (0, unreactive)

PeriodsPeriods are horizontal rows on the periodic table. are horizontal rows on the periodic table.

INC

RE

AS

ING

RE

AC

TIV

ITY

Where are the following?

• Atomic Number

• Period

• Group/Family

• Metals

• Non-metals

• Transition metals

• Metalloids

• Alkali metals

• Alkaline earth metals

• Halogens

• Noble gases

Periodic Table & Ion Formation:Periodic Table & Ion Formation:

Ions: Ions: Atoms that gain and lose electrons to become oms that gain and lose electrons to become stable (full valence shells).stable (full valence shells). 1. Cations: 1. Cations: metals that lose electrons & form metals that lose electrons & form

positive ions (Napositive ions (Na++)) Multivalent:Multivalent: Some metals can have more than Some metals can have more than

one charge (Feone charge (Fe2+2+ or Fe or Fe3+3+).). 2. Anions:2. Anions: Non-metals gain electrons & form Non-metals gain electrons & form

negative ions (Onegative ions (O-2-2))

Bohr Diagrams:Bohr Diagrams:

Bohr diagrams show how many electrons Bohr diagrams show how many electrons appear in each electron shell around an appear in each electron shell around an atom. (2, 8, 8, 18, 18)atom. (2, 8, 8, 18, 18) Valence electrons:Valence electrons: electrons in the outermost electrons in the outermost

shell ONLY.shell ONLY. If the valence shell is full = stableIf the valence shell is full = stable If the valence shell is not full = reactiveIf the valence shell is not full = reactive

What element is this?

Bohr Diagrams

•It has 2 + 8 + 8 = 18 electrons, and therefore 18 protons

•It has 8 electrons in the outer (valence) shell

18 p

22 n

Argon!

Ionic Bonds:Ionic Bonds: Formed between Metals (cations) & non-metals (anions).Formed between Metals (cations) & non-metals (anions). Valence electrons are transferred from metal to nonmetal.Valence electrons are transferred from metal to nonmetal.

Eg. LiEg. Li22OO

Lithium Oxygen

+

Electrons are transferred from the cations to the anion

Li+ O2- Li+

Lithium oxide,Li2O

Formed between two or more non-metalsFormed between two or more non-metals Valence electrons are shared between atomsValence electrons are shared between atoms Eg. HFEg. HF

Covalent Bonds:Covalent Bonds:

Hydrogen Fluorine

+

Electrons are shared

Hydrogen fluoride

Lewis Diagrams:Lewis Diagrams:

Only valence electrons are shownOnly valence electrons are shown

Dots representing valence electrons are placed around Dots representing valence electrons are placed around the element symbols (on 4 sides, imagine a box the element symbols (on 4 sides, imagine a box around the symbol)around the symbol)

Electron dots are placed singularly, Electron dots are placed singularly, then they are paired.then they are paired.

Ex: Nitrogen atom

Lewis Diagrams for Ions:Lewis Diagrams for Ions:Ex. Nitrogen ion

Remove or add electron dots to Remove or add electron dots to

make full valence shells.make full valence shells. Square brackets and the charge Square brackets and the charge

are placed around each ionare placed around each ion

Be Cl

• ••

••

•

• •

Each beryllium has two electrons to transfer

away, and each chlorine wants one more electron

BeCl Cl• •

• •

• •

• •

• ••

•• •

• •

• ••

••

•

• •

BeCl Cl• •

• •

• •

• •

• ••

••

•

• •

• ••

••

•

• •Since Be2+ wants to

donate 2 electrons and each Cl– wants to accept

only one, two Cl– ions are necessary

The ionic compound Beryllium chloride is

formed

2+–• •

• •

• •

• •

–

Lewis Diagrams For Covalent Bonds:Lewis Diagrams For Covalent Bonds: valence electrons are drawn to show sharing of valence electrons are drawn to show sharing of

electrons.electrons. Remember: All atoms “like” to have a full valence shellRemember: All atoms “like” to have a full valence shell The shared pairs (“bonding pairs”) of electrons are The shared pairs (“bonding pairs”) of electrons are

usually drawn as a straight lineusually drawn as a straight line ““lone pairs” are the electrons not sharedlone pairs” are the electrons not shared