WHAT DO YOU THINK ATOMS WHAT DO YOU THINK ATOMS LOOK LIKE?LOOK LIKE?

• Draw what you think atoms look Draw what you think atoms look likelike

• Why do you think they look like Why do you think they look like this?this?

HISTORY OF THE ATOMHISTORY OF THE ATOM

460 BC Democritus develops the idea of atoms

he pounded up materials in his

pestle and mortar until he had

reduced them to smaller and

smaller particles which he called

ATOMAATOMA

(greek for indivisible)

HISTORY OF THE ATOMHISTORY OF THE ATOM

1898 Joseph John Thompson

found that atoms could sometimes

eject a far smaller negative

particle which he called an

ELECTRONELECTRON

HISTORY OF THE ATOMHISTORY OF THE ATOM

1910 Ernest Rutherford

they fired Helium nuclei at a piece

of gold foil which was only a few

atoms thick.

they found that although most of

them passed through. About 1 in

10,000 hithttp://micro.magnet.fsu.edu/electromag/java/rutherford/

HELIUM ATOM

+N

N

+-

-

proton

electron

neutron

Shell

What do these particles consist of?

ATOMIC STRUCTUREATOMIC STRUCTURE

Particle

proton

neutron

electron

Charge

+ ve charge

-ve charge

No charge

1

1

nil

Mass

ATOMIC PARTICLES ARE VERY SMALLATOMIC PARTICLES ARE VERY SMALL

SIZE OF ATOMS ANALOGYSIZE OF ATOMS ANALOGY

Atom = Skydome, Toronto

Nucleus = baseball

Protons = marbles inside baseball

Electrons = mosquitoes buzzing around baseball

1. Draw a diagram showing the location of the three types of particles in an atom.

2. Name each type of atomic particle

3. Write the charge of each atomic particle

WHAT DO ATOMS LOOK LIKE?WHAT DO ATOMS LOOK LIKE?

http://daveovergaard.pbworks.com/w/page/50839329/What%20do%20atoms%20look%20like

ATOMIC STRUCTUREATOMIC STRUCTURE

= number of protons in an atom

= number of protons and neutrons in an atom

HeHe22

44 Atomic mass

Atomic number

number of electrons = number of protons

ATOMIC STRUCTUREATOMIC STRUCTURE

ATOMIC STRUCTUREATOMIC STRUCTURE

What is the atomic number of H (hydrogen)?

What is the atomic mass of H (hydrogen)?

How many electrons and protons are in hydrogen atoms?

What would it look like?

ATOMIC STRUCTUREATOMIC STRUCTURE

What is the atomic number of Li (lithium)?

What is the atomic mass of Li (lithium)?

How many electrons and protons are in lithium atoms?

What would it look like?

QUIZ QUESTION:QUIZ QUESTION:

1. Atomic mass is the number of __________ and ___________ in an atom

2. Atomic number is the number of ___________ in an atom

3. How many protons are in this atom?4. What is the overall charge of this atom?5. What element is this atom?

ATOMIC STRUCTUREATOMIC STRUCTURE

Electrons are arranged in Energy Levels

or Shells around the nucleus of an atom.

• first shell a maximum of 2 electrons

• second shell a maximum of 8

electrons

• third shell a maximum of 8

electrons

ATOMIC ENERGY LEVELSATOMIC ENERGY LEVELS

ATOMIC STRUCTUREATOMIC STRUCTURE

There are two ways to represent the atomic

structure of an element or compound;

1. Electronic Configuration

2. Dot & Cross Diagrams

ELECTRONIC CONFIGURATIONELECTRONIC CONFIGURATION

With electronic configuration elements are

represented numerically by the number of

electrons in their shells and number of shells. For

example;

N

Nitrogen

7

14

2 in 1st shell

5 in 2nd shell

configuration = 2 , 5

2 + 5 = 7

ELECTRONIC CONFIGURATIONELECTRONIC CONFIGURATION

Write the electronic configuration for the following elements;

Ca O

Cl Si

Na20

40

11

23

8

17

16

35

14

28B

11

5

a) b) c)

d) e) f)

2,8,8,2 2,8,1

2,8,7 2,8,4 2,3

2,6

DOT & CROSS DIAGRAMSDOT & CROSS DIAGRAMS

With Dot & Cross diagrams elements and

compounds are represented by Dots or Crosses to

show electrons, and circles to show the shells. For

example;

Nitrogen N XX X

X

XX

X

N7

14

DOT & CROSS DIAGRAMSDOT & CROSS DIAGRAMS

Draw the Dot & Cross diagrams for the following elements;

O Cl8 17

16 35a) b)

O

X

XX

X

X

X

X

X

Cl

X

X

X

X X

X

XX

X

X

X

X

X

XX

X

X

X

SUMMARYSUMMARY

1. The Atomic Number of an atom = number of

protons in the nucleus.

2. The Atomic Mass of an atom = number of

Protons + Neutrons in the nucleus.

3. The number of Protons = Number of Electrons.

4. Electrons orbit the nucleus in shells.

5. Each shell can only carry a set number of electrons.