Announcements• Make corrections to your test.

Your new grade will count as a quiz grade.– Due Monday

• Missed work folder moved to 104, yellow bulletin board

• Get extra help when you need it! – 3rd floor office, Mondays/Thursdays

3:30-4:30 or by appointment

• Collected today: Ions Practice worksheet

• I should already have your Week 13 Homework

Why are we doing this?

• Elements in your life?• What are most things made of?• Atoms and ions combine to make

compounds. (December, January…)

• Compounds combine and react to make new compounds. (Next semester)

Bonding

Electronegativity• How strongly an atom attracts other

electrons in a chemical bond• Increases going up a group

– In lower periods, valence electrons are further from the nucleus, less “pull” from the protons

• Increases going across a period– Electrons on the same energy level are

more strongly “pulled” by the nucleus• Same as ionization energy!!

Atomic Radius Increases

Ato

mic R

adiu

s Increases

Electronegativity IncreasesE

lect

ron

egat

ivit

y In

crea

ses

• chemical bond: strong electronic attraction between atoms– decreases the potential energy of

an atom; makes it more stable– only the valence electrons are

involved!

Three Types of Bonds

• Bond type depends on electronegativity (e-neg)1. Ionic Bond: very different e-negs.

one metal, one non-metal

2. Covalent Bond: both e-negs. very hightwo non-metals

3. Metallic Bond: both e-negs. lowone or more metals

MetalsMetals

Non-Non-metalsmetals

CationsCations

AnionsAnions

Low ELow E--negneg

High High EE--negneg

1 from here1 from here

1 from 1 from herehere

Ionic Bond

≥≥2 2 from from herehere

Covalent Bond

≥≥1 from 1 from herehere

Metallic Bond

Ionic Bonds

• metal + non-metal• Low e-neg. + high e-neg.• Transfer e- from one atom to

another.• Form cation + anion• Ions are attracted to one

another

sodium and chlorine

• sodium transfers its electron to chlorine

Na Cl

Ionic or Covalent Bond?• Na and Cl• O and F• Ca and Cl• Mg and Br• N and O• Al and I• O and P• K and O

• Ionic vs. Covalent Bonds: Modeling

Ionic Bond Vocabulary

• Chemical formula: shows the kind and number of atoms in the smallest unit of the compound.– Ex: H2O, NaCl, C6H12O6

• Law of Definite Proportions: In any chemical compound, the masses of the elements are in the same proportions.

• Ex: If you had 100.00 g of magnesium sulfide, you would always have 43.13 g of magnesium and 56.87 g of sulfur.

• Magnesium chloride always has 1 atom of Mg to 2 atoms of chlorine.

• Structure of Ionic Compounds:– Crystal Lattice or Array– LOTS and LOTS of ions all

attracted to one another– Ex: Salt = NaCl– One Na atom for every Cl atom in

a huge lattice

• Formula unit: The formula for an ionic compound.

• The lowest whole-number ratio of ions in the compound.

• Ex: NaCl = 1:1 ratio of sodium to chlorine

• Ex: MgCl2 = 1:2 ratio of magnesium to chlorine

Writing Formulae for Ionic Compounds

Homework

• Polyatomic ions: most covalently bonded, but have an overall electronic charge

Naming Ionic Compounds

• anion ending …ide– Cr(OH)3

– CuF2

– Ca2+ PO43-

• chromium(III)

hydroxide• copper(II) fluoride

• Ca3(PO4)2

– calcium phosphate

Crystal Lattice (Array)

• structure of an ionic bond• each anion is surrounded by

cations and vice versa

Announcements

• Missing work on spreadsheet on yellow bulletin board

• Progress Reports submitted Friday only if your grade is…– Failing– Increased by 10% or more – Decreased by 10% or more

Properties of Ionic Compounds• hard• brittle (break easily)• solid• high melting/boiling points• do not conduct electricity as solids• conduct electricity when dissolved

in water (aq) or molten (melted into a liquid) - electrolyte

• more soluble in water than in other solvents

Ionic Compunds with Transition Metals

Transition Transition MetalsMetals

Transition Metals

• Transition Metals: metals in groups 3-12

• Can form ions with different charges

• Ex: Copper Cu+ Cu2+

• Ex: Iron Fe2+ Fe3+

How do you know which ion is formed?

• Stock System: Indicates which charge a transition metal ion has

• Uses Roman Numerals to show charge– I = 1+– II = 2+– III = 3+– IV = 4+– V = 5+

Oxidation States (Ions) of V

• http://www.youtube.com/watch?v=j-EaUHa_nuk&feature=PlayList&p=7E0E03ABA98A34AD&playnext=1&playnext_from=PL&index=19

• http://www.youtube.com/watch?v=j-EaUHa_nuk&feature=PlayList&p=7E0E03ABA98A34AD&playnext=1&playnext_from=PL&index=19

Some hints:

• Stock system is ONLY used for cations that are transition metals– Cu, Fe, Hg, Pb, Sn, Cr, Mn, Co

• Roman numeral comes AFTER cation.

• Anions NEVER have Roman numerals.

Examples

Covalent Bonding

• two or more non-metals• atoms share some valence

electrons (not transfer)

Covalent Bonding

• two or more non-metals• atoms share some valence

electrons (not transfer)• single covalent bond: shares one

pair of electrons• double: 2 pairs of e-

• triple: 3 pairs of e-

• usually each atom donates (gives) one of each pair of electrons

• dative covalent bond: sometimes one atom donates both electrons

F FElectron PairElectron Pair

Shared by both atomsShared by both atomsEach e- donate by each atomEach e- donate by each atom

• number of bonds formed depends on the number of e- required to fill the valence shell– noble gases = full valence, rarely

form compounds

• octet rule: usually, atoms want 8 valence e- (H, He need 2)

• Ex: C has 4 valence e-– needs 4 more to form a full octet– C forms 4 bonds

• Ex: F has 7 valence e-– needs 1 more to form a full octet– F makes one bond

• Nitrogen?

Bonding between C and F

F

F

F

F C

structural hybrid Lewis

formula diagram diagram

=e- pair F e- C e-

=covalent bond

F

F

F

F CF

F

F

F C

Double Bond

• sharing two pairs of electrons• bonds more strongly than a single

bond

• structural hybrid Lewis

CO O CO OCO O

Triple Bond

• Strongest

NN NN NN

Drawing molecule diagrams

1. Decide how many bonds each atom makes.

2. The central atom is the one that makes the most bonds.

3. Draw with single bonds4. Calculate remaining electrons5. Use remaining electrons

• HCN (hydrogen cyanide) – C=4, N=3, H=1

• HCO2- (methanoate ion)

– H=1, C=4, O=2

Draw structural, hybrid and Lewis structures

• HF

• NH3

• CH4

• CF4

• NO2-

• CHCl3

• NH4+

• H2CO

• SeF2

• “…those sciences are vain and full of errors that are not born of experience, the mother of all certainty.”– Leonardo da Vinci

Length and Strength of Bonds

single double triple

longest shortest

lowest energy highest energy

• covalent bonds = strong• forces between molecules =

weaker– covalent molecules are easily

separated from one another– soft solids– do not conduct electricity– more soluble in non-polar solvents

than in water– low melting/boiling points (liquid or

gas at r.t.p.)

Covalent Molecules

– sometimes, a solid lattice is held together with covalent bonds

• covalent network (giant covalent structures): very hard, very high melting/boiling points– Examples: diamonds and graphite

(both C), SiO2