Unit #4Unit #4

Electron Configuration / Periodic Table

Electron Configuration / Periodic Table

1) Remember: Atoms are:1) Remember: Atoms are:

Nucleus dense positively charged center of the

atom. Accounts for the mass of an atom. Contains both protons and neutrons

Proton positively charged particle (equal to +1) in

the nucleus with a mass of 1 AMU. Approximately equal to 1.67 * 10-24g.

Nucleus dense positively charged center of the

atom. Accounts for the mass of an atom. Contains both protons and neutrons

Proton positively charged particle (equal to +1) in

the nucleus with a mass of 1 AMU. Approximately equal to 1.67 * 10-24g.

Neutronan uncharged particle in the nucleus; same

mass as a proton.

Electronnegatively charged particle (equal to -1) that

orbits the nucleus with an insignificant mass. Approximately equal to 9.11 * 10-28g.

Neutronan uncharged particle in the nucleus; same

mass as a proton.

Electronnegatively charged particle (equal to -1) that

orbits the nucleus with an insignificant mass. Approximately equal to 9.11 * 10-28g.

2) Remember: location and types of electrons

2) Remember: location and types of electrons

Valenceelectrons in the outer most "shell". The

maximum number of these for any atom is 8. (We will later learn that they fill the "s" & "p" sublevels in the highest energy levels).

Coreany electron not considered a valence

electron. In between the nucleus and the outermost "shell".

Valenceelectrons in the outer most "shell". The

maximum number of these for any atom is 8. (We will later learn that they fill the "s" & "p" sublevels in the highest energy levels).

Coreany electron not considered a valence

electron. In between the nucleus and the outermost "shell".

Electron Cloudarea surrounding the nucleus where the electrons can be found. Both valence and core electrons are here. This area is negatively charged. Analogous to clouds surrounding the earth.

Electron Cloudarea surrounding the nucleus where the electrons can be found. Both valence and core electrons are here. This area is negatively charged. Analogous to clouds surrounding the earth.

Electron ConfigurationElectron Configuration

Now we will learn how the electrons are arranged in an atom.

Now we will learn how the electrons are arranged in an atom.

Remember the various atomic theories we learned about in unit #3. Considering

those ideas, what do you think the numbers (and sometimes letters) on the

left-hand edge of the periodic chart represent ?

Remember the various atomic theories we learned about in unit #3. Considering

those ideas, what do you think the numbers (and sometimes letters) on the

left-hand edge of the periodic chart represent ?

Energy Levelrepresents the most probable distance of

the electron from the nucleus of the atom. It is always represented as a positive whole number; 1-7. Electrons in the first energy level have the lowest amount of energy; electrons in the seventh energy level have the most energy. (Sometimes: the energy levels are represented by the letters (from lowest to highest energy) K, L, M, N, O, P, Q.)

Energy Levelrepresents the most probable distance of

the electron from the nucleus of the atom. It is always represented as a positive whole number; 1-7. Electrons in the first energy level have the lowest amount of energy; electrons in the seventh energy level have the most energy. (Sometimes: the energy levels are represented by the letters (from lowest to highest energy) K, L, M, N, O, P, Q.)

Ground statemost stable, lowest energy position of an electron.

Excited stateany position of electron except the ground state. Less stable, higher energy.

Ground statemost stable, lowest energy position of an electron.

Excited stateany position of electron except the ground state. Less stable, higher energy.

Lighting and the chemistry behind the characteristic

colors of some types of light bulbs:

Lighting and the chemistry behind the characteristic

colors of some types of light bulbs:

Law of conservation of energy

energy is neither created nor destroyed, it just changes forms.

Law of conservation of energy

energy is neither created nor destroyed, it just changes forms.

ExamplesExamplesThe sun’s energy is captured by chlorophyll and other accessory pigments

in plants.

The energy is stored in the plant in the form of carbohydrates.

After millions of years, these stored carbohydrates can become fossil fuels.

Humans can burn these fossil fuels to "create" energy. (Heat water to make steam.)

The sun’s energy is captured by chlorophyll and other accessory pigments in plants.

The energy is stored in the plant in the form of carbohydrates.

After millions of years, these stored carbohydrates can become fossil fuels.

Humans can burn these fossil fuels to "create" energy. (Heat water to make steam.)

Example continued…Example continued…

The steam spins turbines that in turn spin generators.

The generators make an electric current.

When the electric current is passed through a "gas" this excites the electrons.

The steam spins turbines that in turn spin generators.

The generators make an electric current.

When the electric current is passed through a "gas" this excites the electrons.

Example continued…Example continued…When the electrons drop back down to their ground state they emit light

of a characteristic color.He = yellow light

Ar = lavender light

Kr = white light

Xe = blue light

Ne = orange / red

Na = yellow / orange

H = red

When the electrons drop back down to their ground state they emit light of a characteristic color.

He = yellow light

Ar = lavender light

Kr = white light

Xe = blue light

Ne = orange / red

Na = yellow / orange

H = red

How it worksHow it works

1p+

ENERGY IN

“LIGHT” OUT

Electron ConfigurationElectron Configuration Particular distribution of electrons among available

"sublevels". Often represented as: 1s22s22p3 (this as you will later learn is the electron configuration of Nitrogen.)

Particular distribution of electrons among available "sublevels". Often represented as: 1s22s22p3 (this as you will later learn is the electron configuration of Nitrogen.)

Sublevel

Indicates the shape of the orbital in which the electrons move. (These are components of a given energy level.) Represented by the letters: s, p, d, and f.

Space orbitalSpace orbital A highly probable location about a nucleus in which an electron may be found. The number

of space orbitals determines the sublevel. Sublevels are composed of “Space Orbitals”. The type of sublevel is determined by the

number of space orbitals.

A highly probable location about a nucleus in which an electron may be found. The number of space orbitals determines the sublevel.

Sublevels are composed of “Space Orbitals”. The type of sublevel is determined by the

number of space orbitals.

All "s", have 1 space orbital. Represented by:

All "p", have 3 space orbitals. Represented by:

All "d", have 5 space orbitals. Represented by:

All "f", have 7 space orbitals. Represented by:

All valence electrons will

ALWAYS be located in ONLY

the "s" and "p" sublevels.

All valence electrons will

ALWAYS be located in ONLY

the "s" and "p" sublevels.

Octet RuleOctet Rule In most cases, chemical bonds form so that each atom has an

octet of electrons in their valence shells. In most cases, chemical bonds form so that each atom has an

octet of electrons in their valence shells.

What is an Octet? Eight of something

Pauli Exclusion PrinciplePauli Exclusion PrincipleRule stating that each space orbital can hold a maximum of 2

electrons and they must have opposite spins.Rule stating that each space orbital can hold a maximum of 2

electrons and they must have opposite spins.

The first electron in a space orbital is represented by drawing an upward pointing arrow in the space orbital.

Example:

The second electron in a space orbital is represented by drawing a downward pointing arrow in the same space orbital. The opposite spins are represented by the arrows with opposite directions.

Example:

If more than one space orbital is in a sublevel; then Hund's Rule will apply.

If more than one space orbital is in a sublevel; then Hund's Rule will apply.

Hund's RuleHund's Rule

When electrons occupy the same sublevel (s, p, d, or f), to

achieve the lowest energy arrangement (most desirable) of

the electrons place the electrons into separate space orbitals,

one at a time until all space orbitals have one electron with all

their spins parallel (going the same direction), before pairing

up any of the electrons.

When electrons occupy the same sublevel (s, p, d, or f), to

achieve the lowest energy arrangement (most desirable) of

the electrons place the electrons into separate space orbitals,

one at a time until all space orbitals have one electron with all

their spins parallel (going the same direction), before pairing

up any of the electrons.

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Aufbau PrincipleAufbau Principle

Scheme used to reproduce the electron configuration of the ground states of atoms by successfully filling subshells with electrons in a specific order.

Scheme used to reproduce the electron configuration of the ground states of atoms by successfully filling subshells with electrons in a specific order.

Remember: electron configuration: particular distribution of electrons among available "sublevels".

Aufbau Principle (con’t.)Aufbau Principle (con’t.)

Also known as the:Also known as the:

The "Order of electron fill".

The "Building up order".

The "Diagonal Rule".

Electrons fill orbitals in a reasonably definite order starting with the lowest energy level.

You must be able to use (and reproduce) the chart that will follow. It will make determination of electron placement much easier.

K

L

M

N

O

P

Q

1s

2s

3s

4s

5s

6s

7s

2p

3p

4p

5p

6p

7p

3d

4d

5d

6d

7d

4f

5f

6f

7f

To use:

Simply start at "1s" and

fill the sublevel according

to Hund's Rule. When a

given sublevel is full,

follow the arrow forward.

When you reach the head

of an arrow, drop down to

the arrow below and

continue to fill sublevels

as per Hund's Rule.

Exceptions to the above "filling pattern" exist.

We will focus only on those within the first 36

elements. As we encounter these exceptions, we will

discuss them since they are often representative of

other elements within the same group.

Exceptions to the above "filling pattern" exist.

We will focus only on those within the first 36

elements. As we encounter these exceptions, we will

discuss them since they are often representative of

other elements within the same group.

1st. Exception1st. Exception

CarbonCarbon (and several other Group IV elements.)

1s22sp3

Orbital DiagramOrbital Diagram

Notation showing how the orbitals of a subshell are occupied by electrons. This follows Hund’s rule.

Example:

Notation showing how the orbitals of a subshell are occupied by electrons. This follows Hund’s rule.

Example:

Remember electron configurations are represented as: 1s22s22p3

Electron Dot NotationElectron Dot Notation

Shows the Element symbol and the valence electrons. Also called "Lewis Symbols". Shows the Element symbol and the valence electrons. Also called "Lewis Symbols".

Symbol- represents the nucleus and the core electrons.Symbol- represents the nucleus and the core electrons.

"Dots"- represent the valence electrons and are shown aseither paired or unpaired.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Represents the first valence "p" space orbital

Represents the third valence "p" space orbital

Represents the second valence "p" space orbital

Represents valence "s" space orbitals

A few periodic short cuts.A few periodic short cuts.

Series / Period Series / Period

horizontal rows on the periodic chart.

All elements in the same series or period are in the same energy level.

Family / Group Family / Group

vertical columns on the periodic chart

All elements in the same family or group have the same number of valence electrons.

Collective group names:Collective group names:

1. Halogens

2. Noble Gases

1. Halogens

2. Noble Gases

Halogens -Halogens -

Very reactive non-metals found in group VII. They have the general formula "X2", where "X" represents the halogen symbol.

Very reactive non-metals found in group VII. They have the general formula "X2", where "X" represents the halogen symbol.

Noble gas - Noble gas -

Any member of the gaseous Group VIII elements that has an octet in their outermost sublevels. They are extremely stable ("satisfied") and therefore do not willingly react with other elements.

Any member of the gaseous Group VIII elements that has an octet in their outermost sublevels. They are extremely stable ("satisfied") and therefore do not willingly react with other elements.

Also called "inert gases"

While originally thought to be totally un-reactive, compounds have been formed with Xenon, Krypton, and Radon.

Although relatively un-reactive, many uses exist:Although relatively un-reactive, many uses exist:

He - fills weather balloons

He, Ne - mixed with O2 for use in artificial atmospheres like those required for deep sea diving.

Ar, Kr, Xe - used to produce inert atmospheres for flashbulbs and aluminum welding (as well as MIG & TIG welding).