Electron Theory

Introduction Structure and Matter Atoms and Molecules Atomic Structure Electron Flow

Introduction

In this section we will discuss the concept

of Matter.

Structure and Matter

Matter

Definition: Anything that occupies space and has mass.

Structure and Matter

Structure and Matter

MatterCan be solid, liquid or gas

Ice Water Air

Structure and Matter

MatterCan be solid, liquid or gasCan be element, compound, or mixture

Structure and Matter

MatterCan be solid, liquid or gasCan be element, compound, or mixture

Element- Is the basic building block of nature Purest form of matter. Can not be divided into simpler

substances (see periodic table) Hydrogen Oxygen Carbon

Structure and Matter

MatterCan be solid, liquid or gasCan be element, compound, or mixture

Element- Is the basic building block of nature Compound- Two or more chemically combined

elements Contain the same proportion throughout

CO2

H2O

Structure and Matter

MatterCan be solid, liquid or gasCan be element, compound, or mixture

Element- Is the basic building block of nature Compound- Two or more chemically combined

elements Mixture- Two or more elements not chemically

combined, (proportion may vary). i.e. Saltwater, Sand and Gravel

Atoms and Molecules

Atom Molecule Molecular Compound Ionic Compound

Atoms and Molecules

Atom- Smallest part of an element that retains the properties of that elementElectronsNeutronsProtons

Electrons

Nucleus containsProtons & neutrons

Atoms and Molecules

AtomElectrons

Negative charge (-)

NeutronsProtons

Electrons

Nucleus containsProtons & neutrons

Atoms and Molecules

AtomElectronsNeutrons

Neutral charge within the nucleus

Protons

Electrons

Nucleus containsProtons & neutrons

Atoms and Molecules

AtomElectronsNeutronsProtons

Positive charge Within nucleus

Electrons

Nucleus containsProtons & neutrons

Atoms

Have a NucleusProtons (positive charge)Neutrons (neutral charge)

Orbiting electrons (negative charge)

Bohr Model (Hydrogen)

Electron

Nucleus (1 proton 1 neutron)

HN=1

Bohr Model (Helium)

Electron

Nucleus (2 protons 2 neutrons)

HeN=1 Electron

Bohr Model (Lithium)

1 valence electron

Nucleus (3 protons 4 neutrons)

Li

N=1

N=2

Bohr Model

The number of electrons in each shell is determined by the formula:

#electrons=2n2

Bohr Model (Copper)

1 valence electron

Nucleus (29 protons 35 neutrons)

Cu

N=1

N=2

N=3

N=4

N=1=2(1)2=2N=2=2(2)2=8N=3=2(3)2=18N=4=2(4)2=32

60

Copper Element

Cu29

63.54Copper

Copper Element

Name

Cu29

63.54Copper

Copper Element

Atomic Number

Name

Cu29

63.54Copper

Copper Element

Atomic Number

Name

Cu29

63.54Copper

ChemicalSymbol

Copper Element

Atomic Number

Name

Cu29

63.54Copper

ChemicalSymbol

Atomic Weight

Electrons charge

The charge of 1 electron = 1.602x10-19 Coulombs

Or 1 Coulomb = 6.24x1018 electrons

Electrons excitation

Electrons will stay in orbit as long as the bond is present between the electron and the protons

Cu

Electrons excitation

When energy is present enough to break the proton and electron’s bond, the electron will release from the atoms outer most (valence) shell.

Cu

Light,Heat,orEMF

Electrons excitation

Direction of electron flow is produced when positive forces are strong enough to pull electrons in a direction.

Cu Cu

+

Cu Cu

-

Electrons excitation

Recall 1 Coulomb = 6.24x1018 electrons

That’s a heck of a lot of electrons!!!!

6,240,000,000,000,000,000 to be exact!!!!

Electrons Flow

Current = The directional flow of electrons from a negative to positive

Electrons Flow

1 Amp = the amount of 1 coulomb of electrons (6.24x1018) crossing an area per second

6.24x1018 electrons/second

_ +

Electrons Flow

This is defined as Current Flow “I” through a conductor

6.24x1018 electrons/second

_ +

Electrons Flow

If we were to say that 2 Amps is flowing in the conductor the # of electrons is (6.24x1018) x 2 and so on…..

6.24x1018 electrons/second

_ +

Electrons Flow

In an ideal world, current flow (electron movement) through a conductor would not have any resistance.

6.24x1018 electrons/second

_ +

Electrons Flow

As we shall see later, this is not the case.

6.24x1018 electrons/second

_ +

Electrons Flow

Until then simply understand current flow is the movement of electrons through a conductive material

6.24x1018 electrons/second

_ +

Practice Problem:

If a copper wire has 50mA of current flowing through it, how many electrons are passing through a single cross-sectional area each second?

Practice Problem:

If a copper wire has 50mA of current flowing through it, how many electrons are passing through a single cross-sectional area each second?

Solution:

(6.24x1018)x.05 = 3.17x1017 electrons/second

End of Presentation