Quantum Model and Electron Configurations

Atomic Models:Old version = Bohr’s

Also known as the planetary atomic model

Describes electron paths as perfect orbits with definite diameters

Good for a visual

New version = Quantum Theory

Most acceptedDiagrams electrons

of a atom based on probability of location at any one time

Bohr’s model: Nucleus is in the center of an atom(like the

sun) and the electrons orbit the nucleus similar to the planets.

Orbits are called shells 1st shell = 2 electrons 2nd shell = 8 electrons 3rd shell = 18 electrons 4th shell = 32 electrons

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QOD VOCAB

What is the approximate mass of an electron?

WHICH IS A TRUE STATEMENT?Compounds can

be broken down (decomposed) by chemical means

Compounds can be decomposed by physical means

0.000549 amu

Quantum THEORY & MechanicsStudy of how light interacts with matter

Quantum Theory:

To better the description of the atomic structure, atoms were exposed to energy (heat) which made the electrons go into what is called the excited state (normal = ground state).

When electrons returned to ground state they emitted energy in the form of light.

Quantum Theory:This method of study is called spectroscopy (spectrum)

Visible light = part of the electromagnetic spectrum between 400-700 nm

Electromagnetic Spectrum

Quantum Theory:Electromagnetic

Spectrum From crest to crest =

frequency which is measured in hertz.

This therefore can be used to identify elements (absorption of energy and color emitted is a fingerprint of an element)Kind of like wearing your team

colors.

            

Team Oxygen

            

Team Carbon

Continuous spectrum of white light

When you pass sunlight through a prism, you get a continuous spectrum of colors like a rainbow.

Line-Emission Spectrum However, when light from Hydrogen

& Helium gases were passed through a prism, they found a dark background with discrete lines.

WHY? This lead to the quantum theory.

H

He

A scientist, Bohr suggested that electrons must exist in Electron Orbitals (shows the most probable area to find an electron of a certain energy.)

So whenever an excited hydrogen atom falls to its ground state or lower energy level, it emits a photon of light, which means that energy levels must be fixed.

Quantum Theory:

Video

Quantum Theory: Electron Configuration

Electrons (e-) of atoms are the basis for every chemical reaction.

In quantum theory, electrons exist in orbitals based on probabilities and these orbitals are arranged within energy levels.

Notice… these orbitals look different from Bohr’s. This diagram is more correct.

Quantum Theory: Electron Configuration

Quantum NumbersQuantum numbers specify the properties of atomic orbitals and the properties of electrons in those orbitals

We will define these numbers & letters.

Example of Quantum #:

3s2

Quantum Theory: Electron Configuration

Principle Quantum Number (n)

Is equal to the number of the energy level (n).

The principle quantum # corresponds to the energy levels 1-7 which is the period number (row) on the periodic table.

Example of Quantum #:

3s2

P

E

R

I

O

D

S

1-7

Blocks and Sublevels

d (n-1)1

2

3

4

5

6

7

4

5

Maximum e- in Energy Levels The maximum number of e- in

any one level is given by the equation 2n2

Calculate the maximum number of electrons that can occupy the 4th principal quantum number (period 4). Solve: Use 2n2

2(4)2

32 electrons total

Quantum Theory: Electron Configuration

N=1, 2e

N=2, 8e

N=3, 18e

N=4, 32e

Sublevels and Orbitals An energy level in made up of

many energy states called sublevels.

The number of sublevels for each energy level is equal to the value of the principal quantum number.

EX: one sublevel in energy level one (period 1) two sublevels in level two (period 2) three sublevels in level three (period 3)

*now lets find out what those sublevels are called…

Quantum Theory: Electron Configuration

Example of Quantum #:

3s2

Sublevels and Orbitals There are 4 sublevels:

s p d f Energy levels and sublevels work together to form

an e- cloud. e- are repelled by one another and move as far

apart as possible. e- clouds take on characteristic shapes called

orbitals.

Quantum Theory: Electron Configuration

Sublevels and Orbitals (notice the shapes)

Orbital Shapess orbitals are spherical. This diagram represents an s orbital.

p orbitals are “dumbbell” shaped. This diagram represents 1 of the 3 types of p orbitals.

d orbitals contains 5 possible orbital shapes.

f orbitals contain 7 possible orbital shapes.

Electrons & OrbitalsOrbitals overlap and change shape as electrons are added.

Each orbital can only hold 2 electrons.

Example of Quantum #:

3s2

Electrons and Orbitals (count

2 electrons per orbit)

s = 2 electrons

p = 2+2+2 =

6 electrons d =

10 f = 14

Orbitals, and Electrons per Sublevel

Principal Quantum

Number (n)Sublevel

# ofOrbitals

# of Electrons per Orbital

1 s 1 2

2 sp

13

26

3 s pd

1 35

2 610

4 s pd f

1 35 7

2 610 14

QOD VOCABThe principal

quantum number corresponds to the:

Which statement is true: The characteristic bright-line spectrum (color) of an element is produced when its electrons… Move to an excited

higher energy state Return to a lower

ground energy state

• Energy Levels• Periods on the periodic table

Distribution of Electrons Atoms are electronically neutral. (for now) There is an electron for every proton in the

nucleus. The larger the atom, the larger the electron

cloud.1. Pauli Exclusion Principle: only two e- can

occupy the same orbital due to the opposite electronic spin .

Electron Filling Diagram

•Sublevels and orbitals are filled as indicated in the diagram.

•Example:

1s2 2s2 2p6 3s2 3p6 4s2 …

Notice… they don’t go in order !

# electrons in the orbital

Sublevel orbital

energy level

Label your blank periodic table.

Read it “like a book”

WRITE the Electron ConfigurationNow try:

1. C2. Kr3. Ca4. Fe5. Hg

QOD VOCABWhat is the total

number of electrons that can be held in the third principal energy level?

Quantum Theory of atomic structure states all except: Electrons orbit the nucleus

in perfect paths Electrons form clouds

based on probability of location

Electron clouds form characteristic shapes due to repelling of negative charges

Electrons occupy the lowest energy levels before moving into higher energy levels

2n2

18

Label your blank periodic table.

Read it “like a book”

DRAW the Electron Configuration

Carbon has 6 e- (same as protons)

Start with lowest energy level and place one electron in each orbital. Spins must be in same direction within orbitals of the same energy level.

If there are remaining e-, pair up singles in same energy level before moving to next highest energy level.

Electron Configuration

1s 2s 2p

Carbon’s electron config. is:

1s2 2s2 2p2

Superscripts total the number of electrons

2 + 2 + 2 = 6

*Notice that you can write the electron configuration based on the orbital diagram.

*When asked to draw or diagram, use arrow configuration.

*When asked to write, use 1s2,2s2… configuration.Last slide

Electron Configuration – Noble Gas Configuration Electron Configuration demonstrates a periodic

trend, so you can write shorthand electron configuration using the electron configuration of the noble gases in Group 18 of the periodic table.

Noble gases have stable configurations.

Noble Gas Configuration When writing shorthand e-

config for an element, refer to the noble gas in the energy level (period) just above the element.

Write the symbol of the noble gas in brackets.

Write out the remaining e-config based on the energy filling diagram.

Electron ConfigurationNa = 1s22s22p63s1

Al = 1s22s22p63s23p1

Ne = 1s22s22p6

Shorthand Electron ConfigurationNa = [Ne] 3s1

Al = [Ne] 3s23p1

Noble Gas Configuration

EX: NaStep 1: Na is in period 3 so refer to the noble

gas in period 2 which is Neon.

Step 2: Write Ne in brackets. [Ne]Step 3: Now write remaining electrons in

standard form. 3s1.Step 4: Combine. [Ne]3s1

Noble Gas ConfigurationEX: BrStep 1: Br is in period 4 so refer to noble gas from

period 3 which is Argon.Step 2: Write in brackets. [Ar]Step 3: Write remaining electrons.

4s23d104p5

Step 4: Combine to form: [Ar] 4s23d104p5

*Check your work: Add the number of electrons from the noble gas (18) to the subscripts of the remaining e-config (17). 18+17=35 which is the electrons for Br.

Nobel Gas Configuration

Now try:1. I2. Kr3. Na4. Cu

Label your blank periodic table.

Read it “like a book”

Electron Configuration with Ions When we write the electron configuration

of a positive ion, we remove one electron for each positive charge:

Na → Na+

1s2 2s2 2p6 3s1 → 1s2 2s2 2p6

When we write the electron configuration of a negative ion, we add one electron for each negative charge:

O → O2-

1s2 2s2 2p4 → 1s2 2s2 2p6

Electron Configuration with IonsNow try:

1. Ca+2

2. Fe-3

Label your blank periodic table.

Read it “like a book”

QOD VOCABWhat element has completely filled 3p orbitals?

Which of the following is the correct name for Ca+1?Calcium isotopeCalcium Calcium ionCalcium with

extra electrons

Argon (Ar)1s2 2s2 2p6 3s2 3p6

Label your blank periodic table.

Read it “like a book”

*

***

**

1

1

2

3

4

5

6

7

32 54 76

1

98

1

10

1

2 1 2 3 4 5

6

1

2

3

4

5

6

1 2 3 4 5 6 7 8 9 10 11 12 13 14

4

5

3

4

5

6

S - Block

D - BlockP - Block

F - Block

4

5

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