John Dalton’s Atomic Theory

1. Matter is composed of atoms. Atoms are composed of protons, neutrons and electrons

2. All atoms of the same element are identical

3. Atoms of different elements are different

4. During a chemical reaction,

atoms combine to form new

products

John Dalton’s Atomic Theory

Each element has a different size because:

# of atoms

# of electrons

Therefore: the higher the atomic number, the bigger the atom of the element will be.

H O H

Organization of Matter

Elements – building blocks of the universe

*made up of atoms

Atoms – smallest unit of matter

*made up of protons, neutrons and electrons

Protons and Neutrons make up the NUCLEUS of the atom

Electrons are located on SHELLS orbiting the nucleus* also called orbitals

Organization of Matter

Molecules – combination of 2 or more atoms

*made up of same OR different atoms (eg. CO2 or O2)

Compound – molecule of different atoms

*H2O, CO2…

Chemical Formula – shows us how many of each atom in a molecule

Periodic Table

A list of elements and their properties

Arranged by

Rows called PERIODS

Columns called FAMILIES

Reading horizontally, the elements atomic numbers increase by 1

Elements in the same family all have the same number of electrons in their outer shells*

* later slides explain

Chemical Symbols

All elements have a chemical symbol

eg. C = Carbon

Na = Sodium*1st letter is CAPITALIZED, 2nd is small – VERY IMPORTANT!!!

Atomic Number.

Tells us the how many protons are in the nucleus

AND

How many electrons on the shells

Shells or Orbitals

Like the moons of a planet,

ELECTRONS orbit the atoms nucleus

Each shell has a maximum capacity

Shell #1 – 2 Electrons

Shell #2 – 8 Electrons

Shell #3 – 8 Electrons

Shell #4 – 8 Electrons

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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.

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.

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.

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.

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

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