Chem A Unit 3

Chem Unit 3

Electrons

Bohr Model

●

Electrons orbit the nucleus at specific, discrete (quantized) energy
levels (n = 1, 2, 3, ...). As electrons are excited, they jump to higher
energy levels.

●

When these electrons relax to lower energy levels, they emit light with
the energy corresponding to the difference between the energy levels.

Multiple Choice

An excited electron decays and emits a(n) ___.

• photon
• electron
• neutron
• proton

Multiple Choice

Which image shows an electron going to a grounded state?

• Image A

• Image B

Light as a Wave

●Electromagnetic Radiation – a form of energy that exhibits wavelike behavior
as it travels through space.

●Wavelength (λ) – the distance between corresponding points on adjacent
waves.
○Measured in meters, centimeters, or nanometers

●Frequency (f) – the number of waves that pass a given point in a specific
time; usually one second.
○Measured in waves/sec or Hertz (1 Hz = 1/s)

Practice Identify the wave with high frequency and the one
with low frequency. Identify the wave with long wavelength
and the one with short wavelength.

__shorter___
Wavelength
__higher___
frequency

__longer___
Wavelength
__lower___
frequency

Multiple Choice

What image shows a wave with a high frequency?

Multiple Choice

What is the difference between a wavelength and the frequency?

• Wavelength is the height of a wave, while frequency is the width of the wave.
• Wavelength is the speed at which a wave travels, while frequency is the amplitude of the wave.
• Wavelength is the time it takes for a wave to complete one cycle, while frequency is the energy of the wave.
• Wavelength is the distance between two consecutive points on a wave, while frequency is the number of complete waves that pass a given point in a second.

Light as a Particle

●Light is emitted in small packets of energy called photons

Atomic Orbitals

●

Atomic Orbitals – Regions of space where electrons are likely to be
found.

●

Schrödinger’s models, stated that instead of electrons having orbits,
electrons occupy orbitals. He also found different types of atomic
orbitals, called sub-shells (sublevels), are available in each
electron/energy shell.

Subshells (aka sublevels) - types of atomic orbitals

• s-subshell – has only one spherical orbital.
• p-subshell – three different dumbbell p-orbitals with the same energy, pointing
along the x-, y-, and z-axes.
• d-subshell – five different d-orbitals (whose shapes are complicated) with the
same energy.
• f-subshell – seven different f-orbitals (whose shapes are complicated) with the
same energy.

Multiple Choice

What is an atomic orbital?

• A subatomic particle found in the nucleus of an atom.
• A chemical bond formed between two atoms.
• A unit of measurement for atomic mass.
• Regions of space where electrons are likely to be found.

Multiple Choice

Which images represents the p-orbital of an atom?

Multiple Choice

Which answer describes the s-orbital of an atom?

• The s-orbital is a dumbbell-shaped orbital that can hold a maximum of 4 electrons.
• The s-orbital is a spherical-shaped orbital that can hold a maximum of 2 electrons.
• The s-orbital is a linear-shaped orbital that can hold a maximum of 1 electron.
• The s-orbital is a pyramid-shaped orbital that can hold a maximum of 3 electrons.

Energy Levels of the Wave-Mechanical Model of the Atom

Principal Energy level (n)

#of sublevels (n)

Sublevels available

1

1

1s

2

2

2s 2p

3

3

3s 3p 3d

4

4

4s 4p 4d 4f

5

5

5s 5p 5d 5f 5g

6

6

6s 6p 6d 6f 6g 6h

7

7

7s 7p 7d 7f 7g 7h 7i

An Electron’s Address

Energy Level

Sublevel
(subshell)

Orbitals

Number of Electrons

1

s

_

2

2

s

_

2

p

_ _ _

6

3

s

_

2

p

_ _ _

6

d

_ _ _ _ _

10

4

s

_

2

p

_ _ _

6

d

_ _ _ _ _

10

f

_ _ _ _ _ _ _

14

Multiple Choice

How many electrons can be held in the s-orbital?

• 8
• 4
• 6
• 2

Multiple Choice

How many subshells are in the n = 5 shell?

• 3
• 7
• 5
• 9

Multiple Choice

How many electrons can fill the 5d subshell?

• 6
• 8
• 4
• 10

Practice

1.

How many subshells are in the n = 5 shell? 5 sublevels

2.

How many orbitals are in the 5d subshell? How many electrons can fill the 5d
subshell? 5d _ _ _ _ _; 10 electrons

3.

How many total orbitals are in the n = 6 shell? How many electrons can fill the
n = 6 shell? 6s_ 6p_ _ _ 6d_ _ _ _ _ 6f_ _ _ _ _ _ _ 6g_ _ _ _ _ _ _ _ _ 6h_ _
_ _ _ _ _ _ _ _ _ (36 orbitals): n2; 2n2 = 36x2 = 72 electrons

Most Probable Location of an Electron

Represent an electron located in an orbital inside of the p
sublevel in the 3rd energy level.

3p ↑ _ _

Represent an electron located in an orbital inside of the d
sublevel in the 4th energy level.

4d

Practice

Write the notation for an electron in the 4th energy level in an f sublevel.

4f ↓ _ _ _ _ _ _

Identify two things wrong with the following:
d should have 5 orbitals (lines) not 4. There
is no 2d. d is the third sublevel, so it will
Start in 3d...

Rules for Electron Configuration

●Pauli Exclusion Principle – in order for 2 electrons to occupy the same
orbital, they must have opposite spins (↑↓)

●Aufbau Principle – electrons enter orbitals of lowest energy first (1s…)

●Hund’s Rule – when electrons occupy orbitals of equal energy, one electron
enters each orbital until all the orbitals contain one electron with parallel spins
( ↑ ↑ ↑ then ↓ ↓ ↓ )

Multiple Choice

Electrons enter orbitals of ____ energy first (1s…).

• equal
• lower
• higher
• random

Multiple Choice

What does Hund’s Rule state?

• Electrons occupy orbitals of different energy levels before pairing up.
• Electrons occupy orbitals in pairs before filling up the next energy level.
• Electrons occupy orbitals randomly without any specific order.
• Electrons occupy orbitals of the same energy level one at a time before pairing up.

Multiple Choice

What does Pauli Exclusion Principle state?

• Electrons in an atom can have the same set of quantum numbers.
• The Pauli Exclusion Principle only applies to protons.
• The Pauli Exclusion Principle only applies to atoms with more than one electron.
• in order for 2 electrons to occupy the same orbital, they must have opposite spins

What rule is being violated?

1.

Hund’s rule (Must put 1 e- in each before doubling)

2.

Aufbau principle (Must fill up one sublevel before moving on)

3.

Aufbau principle (fill order is wrong: 1s, 2s, 2p, 3s)

4.

Hund’s rule (All arrows in a sublevel must go the same way)

5.

Pauli exclusion (Must have two different spins, one up, one
down)

​Electron Configuration

Electron Orbital Notation

Shows all the electrons and their spin

Nitrogen

Magnesium

3s

2p

2p

2s

2s

1s

1s

↑↓

↑↓

↑↓

↑↓

↑

↑

↑

↑↓

↑↓

↑↓

↑↓

Practice

Sulfur Nickel

3d

4s

3p

3p

3s

3s

2p

2p

2s

2s

1s

1s

↑↓

↑↓

↑↓

↑↓

↑↓

↑↓

↑↓

↑↓

↑

↑

↑↓

↑↓

↑↓

↑↓

↑↓

↑↓

↑↓

↑↓

↑↓

↑↓

↑↓

↑↓

↑

↑

Electron Configuration

Symbols and numbers that describe the electrons

Nitrogen

1s2 2s2 2p3

Magnesium
1s2 2s2 2p6 3s2

Practice

Sulfur

1s2 2s2 2p6 3s2 3p4

Nickel

1s2 2s2 2p6 3s2 3p6 4s2 3d8

Xenon

1s2 2s2 2p6 3s2 3p6

Noble Gas Configurations

●Noble Gas Notation
○AKA – kernel notation

○Shorthand form of electron configuration

○How to:
■Find the noble gas of the row above the element

■Place that noble gas in brackets – [ x ]

■Finish the electron configuration for the element after the brackets

■Ex: Selenium
■___1s2 2s2 2p6 3s2 3p64s2 3d10 4p4____

■___[Ar] 4s2 3d10 4p4_____________________

Multiple Choice

What is the noble gas configuration of Nitrogen?

• [He] 2s2 2p3

• 1s2 2s2 2p5
• [H] 2s2 2p3

• 1s2 2s2 2p2

Multiple Choice

Which element is represented by [Ne] 3s2?

• sodium (Na)
• magnesium (Mg)
• calcium (Ca)
• potassium (K)

Noble Gas Configuration aka Short Form Electron Config.

Abbreviated form that uses the previous noble gas to account for the full sublevels

Nitrogen
[He] 2s2 2p3

Magnesium

[Ne] 3s2

Practice

Sulfur

[Ne] 3s2 3p4

Nickel

[Ar] 4s2 3d8

Xenon

[Kr] 5s2 4d10 5p6

Multiple Choice

Review: What are valance electrons?

• Electrons in the nucleus of an atom.
• Electrons in the outermost energy level of an atom.
• Electrons in the innermost energy level of an atom.
• Electrons in the middle energy level of an atom.

Valence Electrons

●Valence electrons determine how atoms bond and react. They are the
electrons found on the outer shell.

●Explain how an element’s position on the Periodic Table can be used to
predict the number of its valence electrons.

Valence Electrons

●Number of electrons in the outer-most shell (energy level)

●Electron Configurations

Valence e-

○Sulfur: _1s2 2s2 2p63s2 3p4 ____

___2+4 = 6 VE____

○Gallium: 1s2 2s2 2p6 3s2 3p64s2 3d104p1

___2+1 = 3 VE____

Multiple Choice

How many valance electrons does Germanium have?

• 8
• 6
• 4
• 2

Oxidation Number

●The charge an atom would have when it gets a full outer shell.

○The atom can get a full outer shell by gaining or losing electrons.

○Atoms will move the least amount of spaces in order to get a full outer shell

■We will only do this for atoms in s and p sublevels.

■Ignore elements in d sublevels.

●Examples:

○Sulfur: ___-2___

○Gallium: ___+3____

○Rubidium: ___+1____

Multiple Choice

What are oxidation numbers?

• Oxidation numbers are the charge an atom would have when it gets a full outer shell.

• Oxidation numbers are only assigned to metals in a chemical compound.
• Oxidation numbers indicate the number of protons in an atom.
• Oxidation numbers are used to determine the color of a chemical compound.

Multiple Choice

What is the oxidation number of potassium?

• +2
• -1
• +1
• 0

Multiple Choice

What is the oxidation number of Neon?

• -1
• +1
• 0
• +2

Multiple Choice

What is the oxidation number of Iodine?

• +1
• +2
• -1
• 0

Multiple Choice

Which part of the periodic table represents the s-orbital?

• Orange

• Blue

• Purple

• Green

Multiple Choice

Which part of the periodic table represents the d-orbital?

• Orange

• Blue

• Purple

• Green

Multiple Choice

Which part of the periodic table represents the p-orbital?

• Orange

• Blue

• Purple

• Green

Multiple Choice

Which orbital is represented by the orange region of the periodic table?

• S

• P

• D

• F