The attraction of opposites

What Is an Ionic Bond?An ionic bond is the attraction of

two oppositely charged ions. These ions combine and the

opposite charges cancel each other out like the electrons and protons of an atom.

Combining the ions of different elements creates new matter that is useful to the world today.

For example, when a sodium atom bonds with a chlorine ion, they form sodium chloride which is table salt.

Electron TransferWhen an atom has less than eight valence electrons it is not chemically stable and must get chemically stable,It will lose electrons or gain electrons to fill its last energy level and therefore become chemically stable.

Ionic Bonding

Metals will always lose electrons to become chemically stableMetals will form positive ions

Non metals will always gain electrons to become chemically stableNonmetals will always form negative ions

Example Of An Ionic BondWhen a sodium atom and a chlorine atom combine, sodium’s one valence electron gets transferred or moved to the chlorine atom. Both atoms are now ions; – sodium is positive and – chlorine is negative. – The ions attract each other and bond.

These two form Sodium Chloride, which is table salt.

Diagram: Na + Cl

Sodium’s 1 valence electron is transferred to Chlorine.

Result: Na + Cl NaCl

Chlorine is stable (8 valence electrons).

Sodium is now stable too (8 valence electrons).

Forming Ionic BondsThings to remember!

An ionic bond is the attraction between two oppositely charged ions.Oppositely charged ions attract each other.Ionic bonds are formed when electrons are taken and not shared.

Pictures of Forming Ionic Bonds

The ions attract each other. Therefore, they bond.

Ionic bonding forms compounds

Ionic bonding doesn’t form moleculesThe oppositely charged ions are attracted to each other – forming very strong bonds!!

Crystal ShapeEvery ion in an ionic bond is attracted to ions near it that have an opposite charge.Because of this, all the ions attract many ions.Therefore, they create a shape.This shape is 3-D and is called the crystal shape.

Characteristic of ionic bonds:

Crystal ShapeIonic solids are generally high melting pointsIonic solids are hard and brittle Ionic solids conduct electricity only when they are dissolved in water

Electrical ConductivityWhen ionic compounds are dissolved in water, they conduct electricity.When they are solid, they don’t conduct.The ions are tightly bound together and have no room to move or let the electricity flow through.When dissolved, the ions move more freely; therefore, electricity can flow through them.

High Melting PointsIonic Bonds are very strong.It takes a lot of heat (energy) to make the particles have enough energy to overcome the attractive forces.Ionic bonds are so strong that all ionic bonds are solids at room temperature.

Elements Which Form This Bond

Metal + Nonmetal = Ionic Bond

Common Ions Which Form This Bond

LithiumSodiumPotassiumCalciumMagnesiumAluminum

OxideFluorideChlorideIodideSulfide

Writing Chemical formulas for ionic compounds.

• Example: • Mg Br

7 valence electrons2 valence electrons

The point of ionic bonding is giving the electron so that Br can become chemically stable, for it to become chemically stable, the valence electron has to be 8.

BrThe reason you have to double the Br is because you cant have more than 8 valence electrons in one element

The Chemical formula for this compound is MgBr2. This translates to one magnesium and two Bromide.

Pictures Of Atomic Bonds

Ionic Bond

Covalent Bond

Polyatomic IonsA Polyatomic ion is an electrically charged collection of more than one atom. Polyatomic ions usually have a charge because the collection of atoms has either gained or lost an electron. Each polyatomic ion has an overall positive or negative charge. If a polyatomic ion combines with an ion of an opposite charge, an ionic compound forms.

Example of A Polyatomic Ion

Carbonate ion (CO32-), made of 1 carbon atom & 3 oxygen atoms. Combines with Calcium ion (Ca2+). Makes Calcium Carbonate (CaCO3)

Did You Understand?What properties do ionic compounds have?Why are ions in ionic compounds attracted to each other?What are polyatomic ions?What is the process of Ionic Bonding?Summary: What is an Ionic Bond?

Covalent Bonding

Covalent BondingCovalent Bond: – a bond formed by the sharing of

electrons between atoms. (does NOT form charges)

– Made up of nonmetalsMolecule: a neutral group of atoms joined together by covalent bonds. (Compounds formed with ionic bonds do NOT have molecules) Molecular Formula: chemical formula for a molecular compound. It shows how many atoms of each element a molecule contains.

Covalent BondingExamples: ascorbic acid (vitamin C): C6H8O6

C_____, H_____, O_____,

trinitrotoluene (TNT): C7H5N3O6

C_____, H_____, N_____, O_____,

6 8 6

7 5 3 6

Molecular Nomenclature

Prefix System (binary compounds)

1. Less electronegative atom comes first.

2. Add prefixes to indicate # of atoms. Omit mono- prefix on first element.

3. Change the ending of the second element to -ide.

most

PREFIXmono-di-tri-tetra-penta-hexa-hepta-octa-nona-deca-

NUMBER123456789

10

Molecular Nomenclature

P2O5 =CO2 =CO =

N2O =

diphosphorus pentoxidecarbon dioxidecarbon monoxidedinitrogen monoxide

Naming Covalent Binary Compounds

PCl5N2H4

Cl2O7

IO2

phosphorous pentachloride = dinitrogen tetrahydride

=dichlorine heptaoxide =iodine dioxide =

Lewis StructuresElectron Dot Diagrams–show valence e- as dots–distribute dots like arrows in an orbital diagram

–4 sides = 1 s-orbital, 3 p-orbitals–EX: oxygen

2s 2pO

X

Lewis StructuresOctet Rule–Most atoms form bonds in order to obtain 8 valence e-

–Full energy level stability ~ Noble Gases

Ne

Diatomic Molecules• Diatomic Molecule: a molecule

consisting of two atoms.• Diatomic molecules in nature:

H2, N2, O2, F2, Cl2, Br2, I2

“Professor BrINClHOF”

#s of Covalent Bonds

Cl ClO O

N N

Single Bond: 2 e- shared

Double Bond: 4 e- shared

Triple Bond: 6 e- shared

Polyatomic Ions and covalent bonding “CHLORATE”

O Cl OO

Chlorine has 7 valence e-

Each oxygen has 6 valence e-

When ClO3 comes together they form 3 single covalent bonds

One additional electron completes chlorine with a full valence shell, making this a covalently bonded group with an ionic charge of -1

-1

O C OO

Polyatomic Ions and covalent bonding “CARBONATE”

Carbon has 4 valence e-

-2

Each oxygen has 6 valence e-

When CO3 comes together they form 2 single covalent bonds and 1 double covalent bond

Two additional electrons completes carbon with a full valence shell, making this a covalently bonded group with an ionic charge of -2

O O P O O

Polyatomic Ions and covalent bonding “PHOSPHATE”

Phosphorus has 5 valence e--

3Each oxygen has 6 valence e-

When PO4 comes together they form 3 single covalent bonds

Three additional electrons completes phosphorus with a full valence shell, making this a covalently bonded group with an ionic charge of -3

Polarity

Bond PolarityMost bonds are a blend of ionic and covalent characteristics.

Difference in electronegativity determines bond type.

E difference: 0.0-0.4

E difference: 0.4-1.7

E difference: >1.7

Bond PolarityElectronegativity–Attraction an atom has for a shared

pair of electrons.–higher e-neg atom -

–lower e-neg atom +

Bond PolarityElectronegativity Trend – Increases up and to the right.

Table of Electronegativity

Nonpolar Covalent Bond–e- are shared equally–symmetrical e- density–usually identical atoms

Bond Polarity

+ -

Bond Polarity

Polar Covalent Bond–e- are shared unequally–asymmetrical e- density– results in partial charges (dipole)

• Nonpolar– e- shared equally

• Polar– e- shared

unequally

• Ionic– e- transferred

Bond Polarity

E difference: >1.7

E difference: 0.4-1.7

E difference: 0.0-0.4

+ -

+

Bond PolarityNonpolar Covalent – equally shared e-

Polar Covalent - partial charges, e- shared unequally

Polar MoleculeOne end of the molecule is slightly negative and the other end is slightly positiveCaused by the presence of a polar bond in the molecule. (structure is not symmetrical)A molecule that has two poles is called a dipolar molecule, or dipole.

+ FH

Self TestIs CO2 a covalent or ionic compound?What is CO2 ’s name?What is the electronegativity difference between C and O?Does CO2 have polar bonds?Is CO2 a polar molecule overall?

. .O. .

C: :O

Quiz - answer the following on a sheet of paper1. The following ball-and-stick molecular model is a

representation of thalidomide, a drug that causes birth defects when taken by expectant mothers but is valuable for its use against leprosy. The lines indicate only the connections between atoms, not whether the bonds are single, double, or triple (red = O, gray = C, blue = N, ivory = H):

(a) What is the molecular formula of thalidomide?

2. Above is a ball-and-stick molecular model representation of acetaminophen, the active ingredient in such over-the-counter headache remedies as Tylenol (red = O, gray = C, blue = N, ivory = H):(a) What is the molecular formula of acetaminophen?