Atomic Structure

Atomic Structure

• Elements• Atoms• Components of an Atom• Atomic Number• Periodic Table of Elements• Electrons• Electron Orbits

Elements

The simplest form of matter

Atoms

The smallest piece of an element that contains all properties of that element

Components of an Atom

Nucleus

The center portion of an atom containing the protons and neutrons

Protons

Positively charged atomic particles

Neutrons

Uncharged atomic particles

Atomic Number

The atomic number is equal to the number of protons in the nucleus of an atom.

The atomic number identifies the element.

How many protons are in this nucleus?

Periodic Table of Elements

Which element has 4 protons?NASA

Electrons

For this unit, we mainly care about electrons in atoms.

Why?

It is important to understand the “how and why” of the movement of electrons to understand electricity.

Electrons

Negatively charged particles

Electrons

3D 2D

Models of the Atom

Bohr’s Model

Electrons

• The electrons reside in the electron cloud

• The clouds are divided into 7 energy levels

• Electrons “reside” in lowest energy levels whenever possible.

ElectronsAreas within each energy level where electrons move around the nucleus of an atom are known as Electron Orbitals.

There are four different type of orbitals, each type able to contain different numbers of electrons

Sharp DiffusePrincipal Fundamental

ElectronsEnergy Level

Types of Orbitals

Maximum Electrons

1 1 (S)

2

2 2 (S & P)

8

3 3 (S, P, D)

18

4 4 (S, P, D & F)

32

5 4(S, P, D & F)

32

6 3(S, P, D)

18

7 2(S & P)

8

Types of Orbitals

S orbitals can hold up to 2 electrons

P orbitals can hold up to 6 electrons

D orbitals can hold up to 10 electrons

F orbitals can hold up to 14 electrons

Electrons

Electrons will not completely fill all the orbitals in an energy level before moving up to another level. Because of this,

There are never more than 8 electrons in the highest energy level!

The electrons in the highest energy level of an atom are called the Valence Electrons

Orbital Filling order:1s2s2p3s3p4s3d4p5s4d5p6s4f5d6p7s5f6d7p

Electron Orbits

Atoms work to have their valence level either filled (8) or empty(0) of electrons.

How many electrons are in the valence level?

1

Copper has a loose hold on this electron, so it can easily be moved

Electron Orbits

Atoms like to have their valence level either filled (8) or empty(0) of electrons.

How many electrons are in the valence level?

6

Sulfur has space to gain two electrons in its valence level.

What does all this have to do with Electricity?

The number of valence electrons in an atom will determine if an element will allow electricity to flow.

The ability of an atom to draw electrons to itself (away from its neighbors) is called Electronegativity.

Conductors and Insulators

Conductors Insulators

Electrons flow easily between atoms

1-3 valence electrons in outer orbit

Low Electronegativity

Good Conductors: Silver, Copper, Gold, Aluminum . . .

Electron flow is difficult between atoms

5-8 valence electrons in outer orbit

High Electronegativity

Examples: Mica, Glass, Rubber, Plastic . . .

Conductors and Insulators

Identify conductors and insulators

Conductors Insulators

Metals, Non-Metals, & Metalloids

Metals, Non-Metals, & Metalloids

Combination of metal and non-metal properties

Conduct heat & electricity better than insulators, but not as good as metals

Solids

Semi-conductors

Poor Conductors

Good Insulators

Dull Luster

Brittle

Low Density

Melt at lower temps

High Electronegativity

Good Conductors

Poor Insulators

Shiny

Malleable

High Density

Low Electronegativity

Semiconductors

•Include Carbon, Germanium, and Silicon•Contain 4 valence electrons•Neither a good insulator, nor a good conductor, but can be made a better conductor through doping.•Needed for transistors and microchips•Silicon is most often used in electronic applications•Silicon is an insulator at room temperature but becomes a conductor when heated

Electron Flow in Conductors

An atom will lose a valence electron when “pushed” by an electron from another atom.

Electron Flow

Electricity is created as electrons collide and transfer from atom to atom.

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Image Resources

Microsoft, Inc. (2008). Clip Art. Retrieved September 10, 2008, from http://office.microsoft.com/en-us/clipart/default.aspx

National Aeronautics and Space Administration (NASA). (n.d.). Genesis: Search for origins. Retrieved September 10, 2008, from http://genesismission.jpl.nasa.gov/educate/scimodule/cosmic/ptable.html