Practice Valence Electron in Chemistry

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

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Quick Recap

An electron residing in the outermost (highest-energy) occupied shell of an atom, available for participation in chemical bonding through sharing, gaining, or losing.

The electrons that 'reach out' to other atoms. These do the bonding.

Showing a random 20 of 50 problems.

Example 1

medium
Why do transition metals like iron not always follow the simple group-number valence rule?

Example 2

challenge
An element forms an oxide X2O\text{X}_2\text{O} and a chloride XCl. How many valence electrons does X have?

Example 3

medium
Why are oxygen and sulfur similar in chemical behavior?

Example 4

easy
Determine the number of valence electrons for: (a) carbon, (b) sulfur, (c) argon.

Example 5

hard
An ion X2−\text{X}^{2-} has electron configuration [Ne]3s23p6[Ne]3s^2 3p^6. Identify X and its valence electrons in neutral form.

Example 6

easy
How many valence electrons does aluminum (group 13) have?

Example 7

hard
How many valence electrons does the NH4+\text{NH}_4^+ ion have in total?

Example 8

easy
How many valence electrons does carbon (group 14) have?

Example 9

medium
Sulfur (group 16) and oxygen (group 16) behave similarly. How many valence electrons drive this, and what anion charge results?

Example 10

medium
Sodium has electron arrangement 2,8,1. How many valence electrons does it have, and is it more likely to lose one electron or gain seven?

Example 11

medium
Which element has 5 valence electrons in period 3?

Example 12

easy
How many valence electrons does nitrogen (Z=7Z = 7) have?

Example 13

easy
Helium has ____ valence electrons.

Example 14

hard
Why is the second ionization energy of sodium so much higher than the first?

Example 15

medium
Explain why elements in Group 17 (halogens) are highly reactive, using the concept of valence electrons.

Example 16

medium
Which has more valence electrons: N3−\text{N}^{3-} or N?

Example 17

hard
Predict the formula of the compound formed between magnesium and nitrogen using valence electrons.

Example 18

hard
Determine the total valence electrons in the CO32−\text{CO}_3^{2-} ion.

Example 19

medium
An atom has electron arrangement 2, 8, 4. How many valence electrons does it have, and what element is it?

Example 20

easy
How many valence electrons does phosphorus (group 15) have?
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