Chapter 5 – Atoms & Chapter 5 – Atoms & BondingBonding

Electron ShellsElectron Shells Electrons aren’t the Electrons aren’t the

same distance from the same distance from the nucleus. They are nucleus. They are arranged in arranged in shellsshells or or energy levels.energy levels.

The electrons in the The electrons in the outer shell are called outer shell are called valence electronsvalence electrons

Each shell can hold only Each shell can hold only a certain number of a certain number of electrons. electrons.

ShellsShells First shell = 2 First shell = 2

electrons – “the electrons – “the sports car”sports car”

Second shell = 8 Second shell = 8 electrons – “the electrons – “the mini van”mini van”

Third shell= 8 Third shell= 8 electrons – electrons – “another mini van”“another mini van”

Valence Electrons & Valence Electrons & BondingBonding Valence e- = electrons in the outermost

shell responsible for bonding The number of valence e- in an atom of

an element determines many traits of that element, including the ways in which the atom can bond with other atoms

The family # tells you the number of valence electrons for each element in the family (A groups only)

Lets practice!Lets practice! According to the periodic table how According to the periodic table how

many valence electrons do the many valence electrons do the following atoms have:following atoms have: Sodium (Na)Sodium (Na) Oxygen (O)Oxygen (O)

How do you know?How do you know? It’s the same as the family #It’s the same as the family #

Valence Electrons & Valence Electrons & BondingBonding

Atoms are more stable (less likely to Atoms are more stable (less likely to react) when they have react) when they have 88 valence valence electronselectrons

Atoms can Atoms can gaingain or or loselose electrons in electrons in order to have 8 valence electronsorder to have 8 valence electrons

Chemical BondChemical Bond – the force of – the force of attraction that holds two atoms attraction that holds two atoms togethertogether

Valence Electrons & Valence Electrons & BondingBonding

Electron DotElectron Dot Diagram – includes Diagram – includes the symbol for the element the symbol for the element surrounded by dots…the dots show surrounded by dots…the dots show the valence electronsthe valence electrons

Section 3 - Covalent BondsSection 3 - Covalent Bonds

Standards Standards 3.b – Students know that compounds 3.b – Students know that compounds

are formed by combining two or more are formed by combining two or more different elements and that compounds different elements and that compounds have properties that are different from have properties that are different from their constituent elements.their constituent elements.

7.c – Students know substances can be 7.c – Students know substances can be classified by their properties, including classified by their properties, including their melting temperature, density, their melting temperature, density, hardness and thermal and electrical hardness and thermal and electrical conductivityconductivity

Chapter 5 – Atoms & Chapter 5 – Atoms & BondingBonding

Electron SharingElectron Sharing Atoms can share valence e- to fill the

outer shell. Non-metals tend to make covalent bonds. Covalent Bond – a chemical bond formed

when two atoms share electrons Ex: H22O Cl2

Drawing covalent BondsDrawing covalent Bonds We can use electron dot diagrams to set up an atom to have 8

valence electrons Electrons can be shared in order to fulfill the octet rule (8 valence

electrons) Draw an electron dot diagram for Oxygen in black: Draw 2 Hydrogen atoms electron dot diagrams in red: Circle the shared electrons for each atom:

How many Bonds?How many Bonds? Atoms can share more

than one pair of electrons.

Double Bond – two pairs of electrons being shared between two atoms

Triple Bond – three pairs of electrons being shared between two atoms

Section 2 – Ionic BondsSection 2 – Ionic Bonds

StandardsStandards 3.b – Students know that compounds 3.b – Students know that compounds

are formed by combining two or more are formed by combining two or more different elements and that compounds different elements and that compounds have properties that are different from have properties that are different from their constituent elements.their constituent elements.

3.c – Students know that atoms and 3.c – Students know that atoms and molecules form solids by building up molecules form solids by building up repeating patterns, such as the crystal repeating patterns, such as the crystal structure of NaCl or long-chain structure of NaCl or long-chain polymerspolymers

Chapter 5 – Atoms & Chapter 5 – Atoms & BondingBonding

Ionic BondingIonic Bonding Atoms can give and take valence Atoms can give and take valence

electrons to fill their outer shell.electrons to fill their outer shell. When an atom loses or gains When an atom loses or gains

electrons, the protons no longer electrons, the protons no longer balance out the electrons, and the balance out the electrons, and the atom becomes positively or atom becomes positively or negatively charged. negatively charged.

IonsIons Ion – an atom or group of atoms that has

become electrically charged When an atom loses an electron it has a When an atom loses an electron it has a

positivepositive charge charge When an atom gains an electron it has a When an atom gains an electron it has a

negativenegative charge chargeElement IonFlouride   F - Chloride   Cl -

Bromide   Br -  Iodide   I -  Bromide   Br -  Oxide   O 2-  Sulfide   S 2-  Nitride   N 3-  Phosphide   P 3-  

10 electrons8 valence e-

Element IonHydrogen   H +

Potassium   K +

Sodium   Na +

Barium  Ba

2+

 

Calcium  Ca

2+

 Magnesiu

m  Mg

2+

Aluminum  

Al 3+  

Boron B 3+ Lithium   Li +  

IonsIons Ionic Bond – the attraction between Ionic Bond – the attraction between

two two oppositelyoppositely charged ions charged ions Ionic bonds form as a result of the Ionic bonds form as a result of the

attraction between attraction between positivepositive and and negativenegative ions ions

Ionic Compound – compound that Ionic Compound – compound that consists of positive and negative consists of positive and negative ionsions

Properties of Ionic Properties of Ionic CompoundsCompounds

The characteristic properties of ionic The characteristic properties of ionic compounds are:compounds are: Crystal ShapeCrystal Shape – orderly 3-D shape– orderly 3-D shape High Melting PointHigh Melting Point – ionic bonds are strong– ionic bonds are strong Electrical ConductivityElectrical Conductivity – when dissolved in – when dissolved in

water, ionic compounds conduct electricitywater, ionic compounds conduct electricity

Chemical Formula & Chemical Formula & NamesNames

Chemical Formula – combination of Chemical Formula – combination of symbols that shows the symbols that shows the ratioratio of elements of elements in a compoundin a compound Ex. MgClEx. MgCl22 or NaCl or K or NaCl or K22SS

When ionic compounds form, the ions come When ionic compounds form, the ions come together in a way that together in a way that balancesbalances out the out the charges on the ionscharges on the ions

Subscript – tells you the Subscript – tells you the ratioratio of elements of elements in the compoundin the compound Ex. MgClEx. MgCl22 - 1 Magnesium ion and 2 Chlorine - 1 Magnesium ion and 2 Chlorine

ionsions

Naming Ionic Naming Ionic CompoundsCompounds

The name of the The name of the positivepositive ion goes first ion goes first Then the name of the Then the name of the negativenegative ion ion

MgMg2+2+ + O + O2-2- MgO MgO Magnesium Magnesium OxOxideide

NaNa++ + CO3 + CO32-2- Na Na22COCO33 Sodium Sodium CarbonateCarbonate

If the negative ion is an element, add If the negative ion is an element, add the ending –idethe ending –ide

If the negative ion is polyatomic, If the negative ion is polyatomic, leave the name the sameleave the name the same

AlAl3+3+ + O + O2–2– AlAl22OO33

Al + O Al + O AlOAlO

CaCa2+2+ + O + O2– 2– CaO CaO

Ca + O Ca + O CaOCaO

MgMg2+2+ + Cl + Cl–– MgClMgCl22

Practice with Ionic Practice with Ionic BondsBonds Examples:Examples:

Na + Cl Na + Cl NaCl NaCl

Mg + Cl Mg + Cl MgClMgCl

NaNa++ + Cl + Cl–– NaClNaCl

IonsIons PolyatomicPolyatomic Ion – ions that are Ion – ions that are

made of more than one atommade of more than one atom Poly means ‘many’Poly means ‘many’ So polyatomic means ‘many atoms’So polyatomic means ‘many atoms’

Element IonAmmonium NH4 +

Bicarbonate   HCO 3-

Nitrate   NO3 -

Carbonate   CO3 2- 

Sulfate SO4 2- 

Phosphate   PO4 3-