# Periodicity of Valence or Oxidation States of Elements

## Introduction to Periodicity of Valence States

Valency is a measure of an element’s ability to combine with other elements. It is defined by the number of electrons an atom needs to gain or lose to achieve a stable electron configuration.

## What is an Oxidation State?

The oxidation state of an atom indicates the number of electrons gained or lost by it.

Valency and oxidation states are key properties of elements, determined by their electron configurations. Valency is the number of electrons an atom must lose or gain to achieve stability, while the oxidation state is the charge of an atom due to electron loss or gain.

## Valency and Oxidation State

Valence electrons are those in an atom’s outermost shell and define its valency. For elements in the s-block and p-block of the periodic table, valency is often calculated as either the number of valence electrons or eight minus that number.

For d-block and f-block elements, valency depends on both valence electrons and electrons in d and f orbitals, with common valencies being 2 and 3.

## Valency of the First 30 Elements in the Periodic Table

Here’s a table listing the valency of the first 30 elements based on their electron configurations:

 Element Symbol Atomic Number Valency Hydrogen H 1 1 Helium He 2 0 Lithium Li 3 1 Beryllium Be 4 2 Boron B 5 3 Carbon C 6 4 Nitrogen N 7 3 Oxygen O 8 2 Fluorine F 9 1 Neon Ne 10 0 Sodium Na 11 1 Magnesium Mg 12 2 Aluminum Al 13 3 Silicon Si 14 4 Phosphorus P 15 3 Sulfur S 16 2 Chlorine Cl 17 1 Argon Ar 18 0 Potassium K 19 1 Calcium Ca 20 2 Scandium Sc 21 3 Titanium Ti 22 4 Vanadium V 23 5,4 Chromium Cr 24 2 Manganese Mn 25 7,4,2 Iron Fe 26 2,3 Cobalt Co 27 3,2 Nickel Ni 28 2 Copper Cu 29 2,1 Zinc Zn 30 2

This table summarizes the valency of the first 30 elements, showing how many electrons each element can gain, lose, or share to form a stable electron configuration.

## Trends in Oxidation States

Across a Period: Moving left to right, the number of valence electrons increases from 1 to 8. Valency increases from 1 to 4 and then decreases to zero when combined with hydrogen or oxygen. For example, in Na2O and F2O, F is more electronegative than O in F2O, giving F a -1 oxidation state and O a +2. In Na2O, O is more electronegative, giving O a -2 oxidation state and Na a +1.

Within a Group: The number of valence electrons remains constant down a group, so elements in the same group have the same valency.

## Guidelines for Assigning Oxidation States

• Elements in their natural form (O2, H2, etc.) have an oxidation state of zero.
• Oxygen typically has an oxidation state of -2, except in peroxides where it is -1.
• Hydrogen is usually +1, but -1 in metal hydrides (e.g., NaH).
• Halogens are generally -1 unless combined with oxygen or each other.
• Alkali metals (Na, K, etc.) have an oxidation state of +1.
• Alkaline earth metals (Mg, Ca, etc.) have an oxidation state of +2.

## Finding Valency of Elements

Valency is determined by the number of electrons in the outer shell. One method to find valency is by consulting the periodic table, where elements in the same group typically have the same valency. For instance, elements in group 8 have a valency of 8, indicating high stability.

By understanding these basic principles, the periodic trends in valency and oxidation states of elements can be easily comprehended.

## FAQs

Why do elements have different oxidation states?2024-07-26T12:11:00+05:30

#### Why do elements have different oxidation states?

Elements have different oxidation states due to their ability to lose or gain different numbers of electrons. This variability depends on the element’s electron configuration and its position in the periodic table.

Can an element have more than one oxidation state?2024-07-26T12:10:26+05:30

#### Can an element have more than one oxidation state?

Yes, many elements can have multiple oxidation states. Transition metals, in particular, often exhibit a variety of oxidation states due to their complex electron configurations.

How do oxidation states vary within a group?2024-07-26T12:10:09+05:30

#### How do oxidation states vary within a group?

Within a group, the number of valence electrons remains the same, so elements in the same group typically exhibit similar valency and oxidation states.

How do oxidation states vary across a period?2024-07-26T12:09:42+05:30

#### How do oxidation states vary across a period?

As you move from left to right across a period, the number of valence electrons increases from 1 to 8. The oxidation state can vary, usually increasing in a similar pattern until reaching group 14, then decreasing.

How do valency and oxidation state relate to each other?2024-07-26T12:09:24+05:30

#### How do valency and oxidation state relate to each other?

Valency is a specific case of oxidation state where the atom’s combining capacity is considered without assigning charges. Oxidation state, on the other hand, always involves the effective charge due to electron gain or loss.

How is valency determined for elements in the periodic table?2024-07-26T12:08:48+05:30

#### How is valency determined for elements in the periodic table?

For s-block and p-block elements, valency is typically the number of valence electrons or eight minus the number of valence electrons. For d-block and f-block elements, valency includes electrons in both valence and d or f orbitals.

What is an oxidation state?2024-07-26T12:08:20+05:30

#### What is an oxidation state?

The oxidation state of an atom indicates the number of electrons an atom has gained or lost. It represents the effective charge of an atom in a compound due to the transfer of electrons.

What is valency?2024-07-26T12:06:59+05:30

#### What is valency?

Valency is the measure of an element’s ability to combine with other elements. It represents the number of electrons an atom needs to gain, lose, or share to achieve a stable electron configuration.