Valence electrons

Valence electrons

By Amy Dahl

What are valence electrons?

Valence electrons are the electrons in the outermost "orbit" around a nucleus.

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Since the orbits increase in energy as they get farther out from the nucleus, that means they are also the electrons in the highest energy level.

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How to count valence electrons

The most common question is, "how many?"

In a Bohr diagram, count the dots in the largest orbit.​​

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In a dot diagram, count the dots.​ ​​

Both diagrams show Cl has 7 valence

electrons​

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Multiple Choice

How many valence electrons are shown in this Bohr diagram?

• 2

• 3

• 5

• 8

Multiple Choice

How many valence electrons?

• 2

• 7

• 8

• 9

Multiple Choice

Recall that valence electrons are the electrons on the orbit (shell) farthest from the nucleus. How many valence electrons?

• 2

• 4

• 6

• 8

Multiple Choice

How many valence electrons?

• 5

• 6

• 7

• 8

Multiple Choice

How many valence electrons?

• 2

• 3

• 4

• 5

Multiple Choice

How many valence electrons?

• 2

• 5

• 8

• 10

Multiple Choice

How many valence electrons?

• 2

• 3

• 4

• 5

Multiple Choice

How many valence electrons?

• 1

• 2

• 4

• 8

Multiple Choice

How many valence electrons?

• 5

• 7

• 3

• 8

Multiple Choice

How many valence electrons?

• 2

• 4

• 6

• 8

Multiple Choice

How many valence electrons?

• 4

• 2

• 7

• 6

We can also find valence electrons from the Periodic Table

The key is to look at the column, or "group"

Looking only at the TALL groups, count from the left.

Or look at the Roman numeral group numbers.​ (IA, IIA, IIIA, etc.)

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All elements in Group IA have one valence electron, all elements in IIA have two, etc.​

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Multiple Choice

How many valence electrons are found in atoms of group 1?

• 7

• 6

• 4

• 1

Multiple Choice

How many valence electrons in Ca?

• 1

• 2

• 8

• 20

Multiple Choice

How many valence electrons in a carbon atom?

• 2

• 4

• 6

• 10

Multiple Choice

How many valence electrons does Nitrogen Have? (this table leaves out the low part in between Groups IIA and IIIA)

Find your element and count columns from the left

• 1 Valence electron

• 2 Valence electron

• 3 Valence electron

• 4 Valence electron

• 5 Valence electron

Multiple Choice

How many valence electrons does Magnesium Have?

• 1 Valence electron

• 2 Valence electron

• 3 Valence electron

• 4 Valence electron

• 5 Valence electron

Multiple Choice

How many valence electrons does fluorine have?

• 1

• 7

• 8

• 9

Multiple Choice

How many valence electrons does Fluorine Have?

• 4 Valence electron

• 5 Valence electron

• 6 Valence electron

• 7 Valence electron

• 8 Valence electron

Finding ion charge--METALS

Metals form ions with charge + (number of valence electrons)

Metals are all elements to the left and below the zigzag line.

Main-group metals (from the tall groups) lose all of their valance electrons.

Since electrons are negative, metal ions get +1 for each electron lost.

Find the number of valence electrons, make it positive, and you have the ion charge.​

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Finding ion charge--NONMETALS

Nonmetals gain electrons, so they become negative (-)

Nonmetals are all elements to the right and above the zigzag line, plus H

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The most valence electrons any element can have is 8​

Nonmetals gain electrons until they have 8.

Subtract their number of valence electrons from 8, make it negative, and you have the ion charge.​

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Multiple Choice

What is the most valence electrons any element can have?

• 8

• 10

• 18

• 100

Multiple Choice

What is the first thing to decide about an element before you can predict the charge?

• What is its atomic number

• What period (row) is it in

• Is it a metal or a nonmetal

• Who discovered it

Multiple Choice

Once we know the number of valence electrons, how do we predict the charge on a metal ion?

• The charge will be + the number of valence electrons

• The charge will be - the number of valence electrons

• Subtract the number of valence electrons from 8 and make it +

• Subtract the number of valence electrons from 8 and make it -

Multiple Choice

Predict the charge on this metal cation

• +1

• -1

• +2

• -2

Multiple Choice

Predict the charge on this metal cation

• +1

• -1

• +2

• -2

Multiple Choice

Predict the charge on this metal cation

• +3

• -3

• +5

• -5

Multiple Choice

Once we know the number of valence electrons, how do we predict the charge on a nonmetal ion?

• The charge will be + the number of valence electrons

• The charge will be - the number of valence electrons

• Subtract the number of valence electrons from 8 and make it +

• Subtract the number of valence electrons from 8 and make it -

Multiple Choice

Predict the charge on this nonmetal anion

• +1

• -1

• +7

• -2

Multiple Choice

Predict the charge on this nonmetal anion

• +3

• -5

• -3

• -4

Multiple Choice

Predict the charge on this nonmetal anion

• +3

• +6

• -6

• -2

Multiple Choice

When this element forms an ion, what will the charge be?

• +1

• +2

• -2

• -1

Multiple Choice

When this element forms an ion, what will the charge be?

• +1

• +2

• -2

• -1

Valence electrons from electron configurations

An electron configuration is a list of all of an element's electrons by energy level and sublevel. They look like this: 1s² 2s² 2p⁶ 3s² 3p³

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​How to determine valence electrons

Subject | Subject

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Here's what you need to know. The big numbers are energy levels.

Valence electrons are in the highest energy level, so ​look for the greatest big number in the electron configuration. It will appear either once or twice, and will always have either s or p in it.

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The small, superscript numbers are numbers of electrons.​ The number of valence electrons is the sum of the small numbers that go with the greatest big numbers you identified.

​Example 1

Subject | Subject

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​Look at the electron configuration 1s² 2s² 2p⁶ 3s² 3p³

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The greatest big number is 3. Two terms contain big 3: ​ 3s² and 3p³.

The small numbers are 2 and 3. Add them together and get 5.

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This element has 5 valence electrons.​

​Example 2

Subject | Subject

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​Look at the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

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The greatest big number is now 4. There is only one 4, and it has s¹ with it.​

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This element has only 1 valence electron.​

Multiple Choice

How many valence electrons?

1s² 2s² 2p⁵

• 2

• 5

• 7

• 8

Multiple Choice

How many valence electrons?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

• 2

• 4

• 6

• 8

Multiple Choice

How many valence electrons?

1s² 2s² 2p⁶ 3s² 3p¹

• 1

• 3

• 8

• 9

Multiple Choice

How many valence electrons?

1s² 2s¹

• 1

• 2

• 3

Poll

How many valence electrons?

1s² 2s² 2p⁶ 3s² 3p⁴

• 2

• 4

• 6

• 8

Multiple Select

What is the greatest number of valence electrons any element can have?

• 8

• 8

• 8

• 8