Early periodic tables

•Dobereiner - early 1800s•Triads- elements with similar properties•Cl, Br, I Ca, Sr, Ba

•Newlands - 1865•62 known elements•Law of Octaves (every 8th element is similar)

Mendeleev’s table - 1869

•By atomic mass•In columns•Predicted missing elements

Moseley’s table – 1910’s

• Working in Rutherford’s lab• Arranged by positive charge he

called atomic number• In rows• Died in WWI

Periodic lawPeriodic law When the elements are arranged

by increasing atomic number,their physical and chemical properties show a repeating pattern

ELEMENTS

• Metals left side of periodic table

• Nonmetals right side of periodic table• Metalloids

along diagonal line

Metals• Lose electrons to make + ions

(cations)• Conduct electricity• Conduct heat• Malleable• Ductile• React with acids• Solids (except ?)• Shiny

Nonmetals• Gain electrons to form – ions (anions)• Do not conduct heat• Do not conduct electricity• Brittle• Solids, liquids or gases• Do not react with acids• Dull

Metalloids• Properties of either• Some gain, some lose electrons• Some conduct, some don’t• Some are malleable, some

brittle• All are solids

Patterns of Atomic NumbersA-6

Family Name Ion Valence electron

• Alkali metals (H) +1 1• Alkaline earth(Be) +2 2 • Aluminum (B) +3 3 • Carbon +/-4 4• Nitrogen -3 5• Oxygen -2 6• Halogen (F) -1 7• Noble(He) 0 8

Trends

•Atomic radius Atomic radius •Melting pointMelting point•ElectronegativityElectronegativity•Oxidation number (charge Oxidation number (charge

on ion)on ion)

Atomic radiusSize of the atom

• Down a familyatoms get bigger

due to more energy levels

• Across a periodAcross a periodatoms get smalleratoms get smallerdue to more pull by protons on due to more pull by protons on

electronselectrons

1. Which is bigger Be or O? Why?1. Which is bigger Be or O? Why?BeBe

2.2. Which is bigger Li or K? Why?Which is bigger Li or K? Why?KK

3.3. Which is smaller B or Al? Why?Which is smaller B or Al? Why?BB

4. Which is smaller F or Cl? Why?4. Which is smaller F or Cl? Why?F

Atomic Radius vs. Atomic Number

0

50

100

150

200

250

300

0 10 20 30 40 50 60 70 80 90 100

Atomic Number

Ato

mic

Rad

ius

Series1

Atomic Size

Li

Na

K RbCs

H NeAr Kr

XeRn

ElectronegativityElectronegativitythe desire of an atom to steal the desire of an atom to steal

another atoms electronanother atoms electron

• Down a familyDown a familyelectronegativity get smallerelectronegativity get smaller

• Across a periodAcross a periodelectronegativity gets largerelectronegativity gets larger

Electronegativity/Atomic # Graph

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 10 20 30 40 50 60 70 80 90 100

Atomic #

Elec

trone

gativ

ity

Series1

Electronegativity

F

Cl BrI

HeNe Ar Kr Xe

Oxidation NumberOxidation NumberCharge on the ionCharge on the ion

MetalsMetalsLose electrons – get smallerLose electrons – get smaller+1, +2, +3, +4+1, +2, +3, +4

Non metals - get biggerNon metals - get biggergain electronsgain electrons

-3, -2, -1-3, -2, -1

Periodic Table:

-4

-3

-2

-1

0

1

2

3

4

5

0 10 20 30 40 50 60 70 80 90 100

Atomic Number

Oxi

datio

n N

Um

ber

Series1

Oxidation Number

C Si

Ca Sr Ba

N PSe

I

Melting PointMelting Point

• Down a familyDown a familymelting point gets smallermelting point gets smaller

• Across a periodAcross a periodmelting point gets largermelting point gets larger

melting point

-1000

-500

0

500

1000

1500

2000

2500

3000

3500

4000

0 10 20 30 40 50 60 70 80 90 100

atomic number

mel

ting

poin

t

melting point

Melting Point

C

SiCa Sr Ba

He Ne Ar Kr Xe

What determines propertiesA - 7

Ionic CompoundsIonic Compounds• Metal/nonmetal steal electronsMetal/nonmetal steal electrons• +/- attraction strong+/- attraction strong• High melting/boiling pointsHigh melting/boiling pointsMoleculesMolecules• Nonmetal/nonmetal share electronsNonmetal/nonmetal share electrons• Weak attractionWeak attraction• Low melting/boiling pointsLow melting/boiling points

Periodic tableA-4

Mendeleev 1869• Organized elements by increasing

atomic mass (weight) in columns• Predicted missing elementsToday’s table• Organized by increasing atomic

number (protons) in rows

1. Which has a smaller melting point N or P?P

2. Which has a smaller melting point Na or Mg?Mg

3. If the melting point of Si is oC and S is oC what would you expect the melting point of P to be?

Octet Rule•An atom will gain or lose

electron to have an octet (or filled) valence energy level