helium atom + n n + - - proton electron neutron shell what do these particles consist of?

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 STRUCTUREATOMIC STRUCTURE

the number of protons in an atom

the number of protons and neutrons in an atom

HeHe22

44 Atomic mass

Atomic number

number of electrons = number of protons

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 STRUCTUREATOMIC STRUCTURE

Three ways to represent the atomic structure

of an element or compound;

1. Lewis Notation

2. Rutherford-Bohr Model

3. The Ball and Stick Model

Determine the number of shells and the number of valence electrons for:

Determine the number of shells and the number of valence electrons for:

• Helium is the exception in Group 8.

• Since it has just one shell, that shell can only fit 2 electrons instead of 8.

• It is in this group because all the elements have a full outer shell.

Lewis Electron Dot Diagrams

Invented by the American chemist, G.N. Lewis.

1. Write the chemical symbol

2. Write the appropriate number of dots in a clockwise manner

Lewis Structures

1) Write the element symbol.

2) Carbon is in the 4th group, so it has 4 valence electrons.

3) Starting at the right, draw 4 electrons, or dots, counter-clockwise around the element symbol.

Lewis Structures

1) Check your work.

2) Using your periodic table, check that Carbon is in the 4th group.

3) You should have 4 total electrons, or dots, drawn in for Carbon.

Lewis Structures

a) H

b) P

c) Ca

d) Ar

e) Cl

f) Al

Lewis Structures

a) H

b) P

c) Ca

d) Ar

e) Cl

f) Al

Lewis Structures

On your worksheet, try these elements on your own:

a) H

b) P

c) Ca

d) Ar

e) Cl

f) Al

Lewis Structures

a) H

b) P

c) Ca

d) Ar

e) Cl

f) Al

Lewis Structures

a) H

b) P

c) Ca

d) Ar

e) Cl

f) Al

Lewis Structures

a) H

b) P

c) Ca

d) Ar

e) Cl

f) Al

Lewis Structures

a) H

b) P

c) Ca

d) Ar

e) Cl

f) Al

BOHR-RUTHERFORD DIAGRAMS

Bohr-Rutherford diagrams should be drawn using the following steps:

Draw the nucleus with the proper number of protons (+1) and neutrons (0).

Draw the first electron shell with the appropriate number of electrons (-1).

BOHR-RUTHERFORD DIAGRAMS

Draw the second valence shell (if applicable) with the appropriate number of electrons (-1).

Continue to draw valence shells with electrons until you have the proper number of electrons for the element.

Example: sulfur

EXAMPLES

• Draw the Bohr-Rutherford Diagram for:

•Mg & Ca

Magnesium (Mg) and calcium (Ca)