Dmitri Mendeleev organized the known elements into a table called the periodic table.

He organized them by their increasing atomic masses.

Today we organize the elements by their

increasing Atomic Number.

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Rows on the periodic table are called periods. All the elements listed in a row belong to the same period. There are 7 (seven) periods.

Columns in the periodic table are called groups or families. All elements in a group have similar properties.

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The columns have been given an Arabic number. The columns are numbered 1 – 18 starting at the left and moving to the right. Please make sure that your periodic table has them numbered like this.

The outer most energy level is usually not full or complete .

Valence electrons are important because they determine how an element will react with other substance.

These electrons in the outer energy level are called Valence electrons.

Valence Electrons

Group 1 and 2 the number of Valence electrons in the outer energy level will match the group number.

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Groups 3 through 12 do not follow any particular rule to determine the number of Valence electrons.

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Group 13 to 18 – The Valence electrons for each of these is the group number less 10. For example Group 14 – 10 = 4 Valence electrons.

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Elements whose atoms gain, lose or share

electrons are reactive and they combine to form the many compounds we use

in our daily lives.

Elements are categorized as metals, nonmetals or

metalloids.

Metals: An element that has luster, is malleable and ductile, and is said to be a good conductor of heat and electricity.

Luster describes the way a surface reflects light…therefore metallic luster would be shiny like a metal object.

Malleable means to be able to press or pound the substance into sheets or different shapes.

What is luster, malleable and ductile?

Ductile means that the substance can be drawn out into thin wires.

Elements are categorized as metals, nonmetals or metalloids (cont’).

Nonmetals: an element that is usually a gas or a brittle solid at room temperature. It is a poor conductor of heat and electricity.

Elements are categorized as metals, nonmetals or metalloids (cont’).

Metalloid: an element that shares some characteristics or properties with both metals and nonmetals.

Group 1 and 2 Elements:

These elements are so reactive that they are only found combined with other

elements in nature.

3

LiLithium6.941

11

NaSodium22.990

19

KPotassium

39.098

37

RbRubidium

85.468

55

CsCesium

132.905

87

FrFrancium

223.020

Group 1: Alkali Metals

• Soft – can be cut with a knife

• Shiny and silver colored

• Low Density (some will even float)

• Most reactive of the metals

• Valence electrons = 1

• Reacts violently with water forming a hydrogen gas

• Compounds from these are very useful such as NaCl

4

BeBeryllium

9.012

12

MgMagnesium

24.305

20

CaCalcium

40.078

38

SrStrontium

87.62

56

Babarium

137.327

88

RaRadium

226

Group 2: Alkaline- Earth Metals

• Very reactive but not as reactive as Alkali Metals.

• Silver colored

• More dense than Group 1 metals

• Valence electrons = 2

• Useful compounds include: Calcium compounds such as cement, plaster, chalk, and YOU.

Group 3 to 12: Transition Metals

• Do not lose their valence electrons as easily as groups 1 & 2.

• Less reactive than Alkali and Alkaline Earth metals

• Shiny

• Good conductors of electricity

•Higher density and melting points (except mercury) than Group 1 and 2

Group 3 to 12: Transition Metals (cont’.)

• Lanthanides: The first row underneath the periodic table: Shiny, reactive, many are used in the production of steel.

• Actinides: The second row underneath the periodic table: These elements are all radioactive and unstable..

Note: Elements found after 94 (Plutonium) are man made and not found in nature

5

BBoron10.811

13

AlAluminum

26.982

31

GaGallium

69.723

49

InIndium

114.818

81

TlThallium

204.383

Group 13: Boron Group

• Reactive

• Valence electrons = 3

• Contains 1 Metalloid and 4 Metals

• Solid at room temperature

• Aluminum is the most abundant in this group and the most common in the Earth’s crust

6

CCarbon12.011

14

SiSilicon28.086

32

GeGermanium

72.64

50

SnTin

118.710

82

PbLead

207.2

Group 14: Carbon Group

• Reactivity varies in this group depending on the element

• Valence electrons = 4

• This group contains 2 metals, 1 nonmetal and 2 metalloids.

• Many forms found uncombined in nature such as diamonds

• Compounds are very useful: proteins, fats, carbohydrates, computer chips.

7

NNitrogen14.007

15

PPhosphorous

30.974

33

AsArsenic

74.922

51

SbAntimony

121.760

83

BiBismuth

208.980

Group 15: Nitrogen Group

• Reactivity varies in this group depending on the element

• Valence electrons = 5

• Group contains 1 metal, 2 Nonmetals, and 2 metalloids

• Phosphorous is very reactive and only found in nature combined with other elements.

• All but nitrogen are solid at room temperature.

• Nitrogen makes up 78% of our atmosphere.

• Generally unreactive.

8

OOxygen15.999

16

SSulfur32.065

34

SeSelenium

78.96

52

TeTellurium127.60

84

PoPolonium

209

Group 16: Oxygen Group

• More reactive than group 15

• Valence electrons = 6

• Group contains 1 Metals, 3 Nonmetals and 1 Metalloids

• Sulfur is found in nature and is used to make sulfuric acid, a very commonly used chemical in industry.

• All but oxygen are solid at room temperature.

• Oxygen makes up 21% of the Earth’s Atmosphere

• Oxygen is very reactive and combines with many other elements especially metals

• Rust is the result of the oxidation of metal.

9

FFluorine18.998

17

ClChlorine

35.453

35

BrBromine79.904

53

IIodine

126.904

85

AtAstatine

210

Group 17: Halogen Group

• Very reactive

• Valence electrons = 7

• Nonmetal group

• Poor Conductors of electricity and heat

• React violently with alkali metals to form salts

• Never found uncombined in nature

• Atoms of these elements only need to gain 1 electron to fill their outer shell

• Chlorine and Iodine are both in this group and can be combined to make disinfectants.

2He

Helium4.003

10

NeNeon

21.180

18

ArArgon39.948

36

KrKrypton83.80

54

XeXenon

131.293

86

RnRadon

222

Group 18: Noble Gas Group

• Non-reactant

• Valence electrons = 8

• Outermost energy shell is full

• Colorless, odorless gases at room temp.

• Under normal conditions they do not react with other elements

• All found on Earth in very small amounts

• Argon is the most common in the group

• Their non-reactivity makes them very useful for light bulbs, helium for blimps and weather balloons.

1H

Hydrogen1.008

Hydrogen Stands Alone:

• Properties do not match the properties of any single group

• Valence Electrons = 1

• Easily looses that one valence electron

• Physical properties are like the nonmetal group

• Most abundant element in the Universe

• Its reactive nature makes it useful as a fuel for rockets.

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