10/10 Understanding Electrons

J.J. Thomson discovered the electron
using a cathode ray tube. The fact
that the ray was deflected by a
magnet meant the beam was made
of particles. The fact that it was
attracted to the positive electric
charge meant that these electrons
were negatively charged (opposites
attract).

Multiple Choice

Who discovered the Electron

• Coach Thompson

• JJ Thompson

• Einstein

• Bill Nye

The atoms of each element behave very differently,
but they all have something very important in
common.

Every atom is made of the same subatomic particles:

Protons

Neutrons

Electrons

Multiple Choice

What are the 3 sub-atomic Particles that make up an atom

• protons, neutrons, and positrons
• electrons, photons, and neutrinos
• protons, electrons, and quarks
• protons, neutrons, and electrons

Protons have a
positive charge.

Neutrons have zero

charge.

They are neutral and not positive

or negative.

Electrons have a
negative charge.

Atom

In order to understand chemistry, you
have to understand the structure of
atoms.

Protons and Neutrons are
joined together in the nucleus.

Electrons fly around freely in
the Electron Cloud.

Multiple Choice

Where are electrons found?

• Inside the nucleolus of the Atom

• Next to the Neutrons

• In a "Cloud" surrounding the Atoms nucleolus.

Atoms have the same
number of protons
and .

electrons

We do not typically
identify an element by
its electrons because
unlike protons,
electrons are gained,
lost and shared between
atoms.

Multiple Choice

Why do we not identify elements by the number of Electrons they hold?

• Because Neutrons are specific to the element

• Electrons are lost and gained, so the number they hold changes constantly

This idea is the foundation of chemistry:

Chemical reactions occur because

atoms gain, lose and share electrons!

Remember: Electrons are
found travelling around
the nucleus in the ELECTRON
CLOUD!

Electrons are not flying around the nucleus
without any order. They organize
themselves into energy levels.

nucleus

1stEnergy Level
2ndEnergy Level
3rdEnergy Level

When we draw atoms,
we always have the
nucleus in the middle.
Each energy level is
shown with a circle.
The black dots
represent the electrons
in that energy level.

Multiple Choice

How many energy levels are incorporated in the periodic table?

• 7
• 12
• 10
• 5

Each energy level is broken down into
sublevels. There are ___ sublevels that
you need to be familiar with. The
higher the energy level, the more
sublevels it will have.

4

Sublevels:

s holds up to 2 electrons
p holds up to 6 electrons
d holds up to 10 electrons
f holds up to 14 electrons

Multiple Choice

How many sub-energy levels are their?

• 3

• 7

• 4

Part of the way the periodic table is arranged is
based on which sublevels are in the outer energy
level of each elements atoms.

s p

d

f

Label the periodic table on your notes.

Multiple Choice

How many electrons can the "d" sub-energy level hold?

• 2

• 6

• 10

• 14

Each energy level has
an additional sublevel
from the energy level
before.

The 1stEnergy Level only has an s sublevel.
The 2ndEnergy Level has an s and p sublevel.

s = 2 electrons
s + p = 2 + 6 = 8 electrons The 3rdEnergy Level has an s, p and d sublevel.
s + p + d = 2 + 6 + 10 = 18 electrons

nucleus

Multiple Choice

The 3rd energy level (3rd Row of the periodic table) has what sub-level capacities?

• s, p, d

• s,p

• s

• s, p, d, f,

The f sublevel does not appear until
the 6thenergy level starts being filled!

s p

d

f

Multiple Choice

In what Row does the "f" sub energy level final hold relevance?

• 6th

• 3rd

• 4th

• 7th

Filling in a electrons:

Phosphorous

Step 1:
Use your periodic table to
determine how many
electrons are in an atom of this
element.

Place up to 2 electrons in the
first level.

Step 2:

If an atom has more than 2
electrons, place up to 8 more
in the second energy level.

Step 3:

If an atom has more than 10
electrons, place up to 18 more
in the third energy level.

Step 4:

15 electrons

Multiple Choice

How many electrons can the third energy level hold?

• 10

• 2

• 18

• 8

Complete the Bohr model diagrams on your

notes by placing the correct number of

electrons in each energy level.

Remember, while atoms begin with the
same number of electrons as protons,

electrons can gain, lose or share electrons.

When you are predicting

how electrons will be

gained, lost or shared, the
total number of electrons is
less important than number

of

valence electrons

Multiple Choice

When Elements are chemically bonding to form a Compound, I should be more concerned about the Total number of Electrons

• True

• False

Valence electrons are the electrons in the

outer energy level.

How many valence electrons do each of

the following atoms have?

1 valence
electron

5 valence
electrons

2 valence
electrons

Decide how many valence electrons are

in each of the atoms on your notes.

8

4

1

7

Valence electrons can be predicted for an
atom by using the periodic table.

This is what the numbers attached to

the A’s and B’s are for!

Multiple Choice

What are the "A's" and "B's" for underneath the Group number on the periodic table?

• Shows the number of Valence Electrons in each group.

• Atomic numbers and atomic masses
• Electron configurations
• Physical and chemical properties

Elements in the same
column or group have
similar physical and
chemical properties

because they all have the

same number of
valence electrons!

All of the
elements
in group I

have

1 valence
electron

Multiple Choice

Why do elements in the same group share the same physical and Chemical properties?

• They share the same number of valence electrons

• They share the same number of Electrons

• They share the same number of Protons

• They share the same number of number of Neutrons.

How many
valence
electrons do
the elements of
group 2 have?

2A = 2

You will ignore the A’s
and B’s. We will learn
what those mean soon.

How many
valence
electrons do
the elements of
group 5 have?

5B = 5

How many
valence
electrons do
the elements
of group 17
have?

7A = 7

How many
valence
electrons do
the elements
of group 14
have?

4A = 4

Use your periodic table to determine
how many valence electrons are in
each of the elements on your notes.

4
8

2

5

2

7

Lewis Dot Diagrams:

Lewis dot structures show the number of
valence electrons in an atom using an atoms
symbol surrounded by dots representing the
valence electrons.

Which Lewis Dot Diagram below accurately

represents hydrogen?
H

H

H

Which Lewis Dot Diagram below accurately

represents nitrogen?

N

N N

Which Lewis Dot Diagram below accurately

represents carbon?

C

C C

For each of the examples on your
notes, circle the Lewis Dot Diagram
that shows the correct number of
valence electrons for each element.

The Octet Rule:

Atoms are most stable when they
have __ valence electrons in their

outer energy level.

8

This means that the s and p

sublevels are both full.

s + p = 2 + 6 = 8 valence electrons

Which group on the periodic table
has 8 electrons in its outer energy
level naturally?

Group 18

The Noble Gases

Group 18 undergoes the fewest chemical
reactions of any of the elements on the
periodic table. They are inert gases. This
is a chemical property that means they
will not react with other substances.

Inert means inactive!

Multiple Choice

Group 18 are called the Noble gasses because

• They have a negative charge.
• They are found in the Earth's core.
• They have a full complement of valence electrons.
• They are highly reactive.

Remember: Group 18 (The Noble Gases)
undergo the fewest reactions because
they have 8 valence electrons.

Neon

Argon

So why is Helium a noble gas?

Since Helium only has 1 energy
level, it only needs 2 electrons to

have a full energy level.

1

2

It will not gain, lose, or share electrons

because its energy level is full. This

makes it an inert noble gas.