mr. ed’s chemistry 9701

Mr. Ed’s Chemistry9701

Term 1Week 2

Chemical Reactivity

How reactive an element is depends on the electron configuration of its atoms.

The electrons in the outer energy level are known as valence electrons

Noble Gas configuration. The magic number 8: octet rule.

Cations! . . . Again.

Group 1, 2, and 3: Easy to loose 1, 2, or 3 electrons. Become positively charged! Group 1 always 1+ charge Group 2 always 2+ Group 3 . . . + ++

Anions . . .

Group 5, 6, and 7: Nitrogen family – Pnictogens. Oxygen family – Chalcogens. Halogens Require 3, 2, or 1 electron for Nobel Gas Negative charged

Attraction

Positive and negative charges attract each other!

Think magnets!

Naming . . . NomenclatureGreek number prefixes.

1. Mono-

2. Di-

3. Tri-

4. Tetra-

5. Penta-

6. Hexa-

7. Hepta-

8. Octa-

9. Nona-

10.Deca-

Binary ionic compounds.

Made of just two elements Is the compound ionic or molecular?Compounds of metals with non-metals Ionic

Binary ionic compounds.

The cation named firstJust the metal’s nameTransition metal must always be

followed by a Roman numeralFollowed by the name of the anion.Mono- is never used for the first part.

Binary ionic compounds.

If there is only one type of compoundGreek numbering is NOT usedCalcium bromide – CaBr2

There is only one bromide of calciumNOT calcium dibromide!

Binary ionic compounds.

For naming anionsElement name and end in –ide

Chlorine Chloride

Bromine Bromide

Oxygen Oxide

Sulfur Sulfide

Nitrogen Nitride

Phosphorus Phosphide

Binary ionic compounds.

Name Sodium chloride Copper(II) chloride Zinc sulfide Magnesium nitride Potassium oxide Aluminum sulfide

Formula

NaCl

CuCl2

ZnS

Mg3N2

K2O

Al2S3

Polyatomic ions.

A group of more than one atom as ion Anions often end in –ate or –ite.

Cations . . . Few Ammonia: NH3 – Ammonium NH4

+

Water: H2O – Hydronium H3O+ Many cations end in -nium

Polyatomic Ionic compounds.

Cation: Again just the metal’s name.Ammonia: NH3 – Ammonium NH4

+

For transition metals: Again Roman numerals for oxidation state.

Second part of: Anion

Ployatomic ionic compounds.

If there is only one type of compoundGreek numbering is NOT usedCalcium carbonate – Ca(NO3)2

There is only one nitrate of calciumNOT calcium dinitrate!

Some common polyatomic cations.

You should know these! End in –ate. OH– – hydroxide NO3

– – nitrate

SO42– – sulfate

CO32– – carbonate

HCO3– – hydrogencarbonate (bicarbonate)

PO43– – phosphate

ClO3– – chlorate

Some more polyanions.

You might see these. NO2

– – Nitrite ion

SO32– – Sulfite ion

PO33– – Phosphite ion

ClO2– – Chlorite

End in -ite

Why do ions form?

The driving force is . . .

ENERGY!

Why do ions form?

Electronegativity A measure of the ability of an atom to attract

electrons (or electron density) towards itself. Proposed by Linus Pauling in 1932. Two: Chemistry and Peace

Why do ions form?

The scale 0.70 to 4.00 0.79 for Cesium . . . The least 3.98 for Fluorine . . . The most Size of atom Charge of nucleus

Viva la difference!

Differences in electronegativity (E.N.) Two atoms of the same element: E.N. = 0 Electron are equally shared

Viva la difference!

Differences in electronegativity (E.N.) Two atoms of the same element: E.N. = 0 Electron are equally shared

Viva la difference!

When both nuclei have same chargeBoth also have same number of e– And same e– configurationAll forces are balancedNon-polar covalent bond

Viva la difference!

Differences in electronegativity (E.N.)Two atoms are of different elements:E.N. difference ≠ 0Electron are not equally sharedMost E.N. atom gets more of the e–

Viva la difference!

Differences in electronegativity (E.N.) E.N. 0.5 Non-polar covalent E.N. 0.5 2.1 Polar covalent E.N. above 2.1 Ionic

Some examples

Hydrogen – 2.20 Alkali metals – least electronegative

Li – 0.98 Rb – 0.82

Na – 0.93 Cs. – 0.79

K – 0.82 Fr – 0.70

Some examples

Hydrogen – 2.20 Alkali metals – least electronegative

Li – 0.98 Rb – 0.82

Na – 0.93 Cs. – 0.79

K – 0.82 Fr – 0.70

Francium:At any given time, as little as 30 g exists throughout the

Earth’s entire crust.

Some examples

Halogens – most electronegative

F – 3.98 I – 2.66

Cl – 3.16 At – 2.2

Br – 2.96

Astatine:Rarest naturally occurring element, less than 25 g

exists at any one time in the Earth’s entire crust.

Some examples

Top six most electronegative

1. F – 3.98 4. N – 3.04

2. O – 3.44 5. Kr* – 3.00

3. Cl – 3.16 6. Br – 2.96

Calculations

Easy – Just subtract E.N. valuesNaClCl = 3.16 and Na = 0.933.16 – 0.93 = 2.23Definitely ionic

Calculations

MgOO = 3.44 and Mg = 1.313.44 – 1.31 = 2.13Also definitely ionic

Calculations

NH3

N = 3.04 and H = 2.203.04 – 2.20 = 0.84Polar covalentH→N←H

↑

H

Calculations

H2OO = 3.44 and H = 2.203.44 – 2.20 = 1.24Strongly polar covalent

Calculations

CH4

C = 2.55 and H = 2.20 2.55 – 2.20 = 0.35 Non-polar covalent

Fortunately . . .

For ionic compounds: No need to calculate.

Simple rules.Compounds of metals: ionicMetal – Non-metalGroups I, II, most of III, Transitions,

bottoms of IV, and V

Fortunately . . .

Compounds of non-metals: Ionic or covalent

Non-metal – Non-metalB, top of groups IV, and V, most of VI,

and group VII.Metal to metal?Alloys

Metal – Metal compounds are rare.

Unfortunately . . .

Naming covalent compoundsLike ionic compounds usually has two

partsFirst part is the LEAST electronegative

elementJust the element’s name

Need no know at least first five most E. N.

Covalent compounds . . .

Naming covalent compoundsLike ionic compounds usually has two

partsFirst part is the LEAST electronegative

elementJust the element’s name

Need no know at least first five most E. N.

Ionic Bonds

Loss of electrons by one atom, gain of electrons by another

Oxidation Is LossReduction Is GainVery strong bonds ElectrostaticCan involve more than one electronMagnetic

OIL RIG

Ionic Solid Structure

Simple repeating structure Ions alternateLatticeGiant structureNo one atom or ion bound to any other

specific atom or ion

Ionic Properties

High melting temperatureHigh boiling temperatureUsually Soluble in polar solventsElectrically conductive when melted or

dissolvedCrystalline – easily cleaved

When do they form?

Great difference between the electro-negativities of elements involved

When little difference . . .

Electro-negativity: A measure of an atom’s tendency to gain

electrons

Related to:Electro-Chemical Series

The more electronegative elements:Upper Right

→The least electronegative:

Lower Left→