Oxidation Number of Tellurium: A Complete Guide for Beginners and Chemistry EnthusiastsTellurium is an element that often gets overlooked, but it plays an important role in chemistry, electronics, and industrial applications. Understanding the oxidation number of tellurium helps chemists predict how it will interact with other elements and form compounds. In this topic, we will explore what tellurium is, its common oxidation states, how to determine these oxidation numbers, and where tellurium is found in everyday life. The language used here is simple and clear, making it accessible for students, educators, and anyone curious about chemistry.
What Is Tellurium?
Tellurium is a metalloid element with the chemical symbol Te and atomic number 52. It has properties of both metals and nonmetals. Tellurium is silvery-white, brittle, and is found in nature often combined with metals in ores. Though not as abundant as other elements, tellurium is used in alloys, semiconductors, and solar cells.
What Is an Oxidation Number?
Before diving into tellurium specifically, it’s important to understand oxidation numbers. The oxidation number, also called the oxidation state, indicates how many electrons an atom gains or loses when forming chemical bonds. A positive number shows electron loss, while a negative number shows electron gain. Oxidation numbers are crucial for balancing chemical reactions and predicting how elements interact in compounds.
Common Oxidation Numbers of Tellurium
Tellurium can exhibit multiple oxidation states, but the most common ones are:
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-2
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+2
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+4
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+6
Each oxidation state corresponds to different types of tellurium compounds and determines how reactive or stable they are.
Why Does Tellurium Have Multiple Oxidation Numbers?
Tellurium’s ability to have different oxidation numbers comes from its position in the periodic table. As a Group 16 element, like sulfur and selenium, tellurium has six valence electrons. It can gain electrons to form negative oxidation states or share/lose electrons to form positive oxidation states. The presence of d-orbitals in heavier elements like tellurium allows for expanded oxidation states, such as +4 and +6.
The -2 Oxidation State of Tellurium
The -2 oxidation number is the most reduced form of tellurium. In this state, tellurium has gained two electrons.
Example: Tellurides
Compounds where tellurium has a -2 oxidation number are called tellurides.
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Example: Sodium telluride (Na₂Te)
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In this compound, two sodium ions (Na⁺) balance one telluride ion (Te²⁻).
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Telluride ions are important in metallurgy and in certain chemical syntheses.
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The +2 Oxidation State of Tellurium
Although less common, tellurium can exhibit a +2 oxidation number. This occurs in compounds where tellurium forms covalent bonds but only loses or shares two electrons.
Example: Tellurium dichloride
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Formula: TeCl₂
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In this compound, tellurium is bonded to two chlorine atoms and has an oxidation number of +2.
The +4 Oxidation State of Tellurium
The +4 oxidation number is one of the most stable and frequently encountered oxidation states of tellurium.
Example: Tellurium dioxide
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Formula: TeO₂
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In this compound, each oxygen atom has an oxidation number of -2, and to balance it out, tellurium must have +4.
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Tellurium dioxide is used in ceramics and glass manufacturing.
The +6 Oxidation State of Tellurium
The +6 oxidation number is the most oxidized form of tellurium. It appears in compounds where tellurium bonds with highly electronegative elements like oxygen or fluorine.
Example: Telluric acid
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Formula: H₆TeO₆ (often written as Te(OH)₆)
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In telluric acid, tellurium has an oxidation number of +6. This compound is used as an oxidizing agent and in analytical chemistry.
How to Determine the Oxidation Number of Tellurium in a Compound
Step 1: Know the oxidation numbers of other elements
Start by identifying the oxidation numbers of the other elements in the compound. For example, oxygen is almost always -2, hydrogen is usually +1, and alkali metals are +1.
Step 2: Set up an equation
Add up all oxidation numbers, including that of tellurium, and set them equal to the charge of the entire molecule or ion.
Step 3: Solve for tellurium
Example:
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In TeO₂, each oxygen is -2.
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There are two oxygens, totaling -4.
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The compound is neutral, so tellurium’s oxidation number must be +4.
Table of Common Tellurium Compounds and Their Oxidation Numbers
| Compound Name | Formula | Tellurium Oxidation Number | Common Uses |
|---|---|---|---|
| Sodium telluride | Na₂Te | -2 | Used in chemical synthesis |
| Tellurium dichloride | TeCl₂ | +2 | Laboratory reagent |
| Tellurium dioxide | TeO₂ | +4 | Used in glass and ceramics |
| Telluric acid | H₆TeO₆ | +6 | Analytical chemistry, oxidizing agent |
Applications of Tellurium Compounds Based on Oxidation Numbers
1. Electronics and Semiconductors
Tellurium compounds, especially those with oxidation numbers of +4 and +6, are used in semiconductors, solar cells, and thermoelectric devices.
2. Metal Alloys
Adding tellurium in the form of tellurides (oxidation number -2) to steel and copper improves machinability and strength.
3. Chemical Industry
Tellurium-based oxidizing agents with higher oxidation numbers are used in refining and purification processes.
The Behavior of Tellurium in Redox Reactions
Tellurium can either gain or lose electrons depending on the chemical environment:
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Reduction: In this process, tellurium gains electrons, moving toward the -2 oxidation state.
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Oxidation: In this process, tellurium loses electrons, moving toward the +4 or +6 oxidation states.
This versatility makes tellurium useful in complex redox reactions in industrial and laboratory settings.
Natural Sources of Tellurium
Tellurium is typically found in:
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Copper ores
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Gold telluride (Calaverite)
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Lead and silver deposits
It is often recovered as a byproduct of copper refining.
Tellurium in Everyday Life
While not as visible as elements like iron or copper, tellurium touches our daily lives in several ways:
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Solar panels: Thin-film solar cells often use cadmium telluride (CdTe).
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Thermoelectric generators: Devices that convert heat into electricity often contain tellurium compounds.
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Optical devices: Tellurium is used in the production of specialized glass and lenses.
Environmental and Safety Considerations
Though tellurium has many benefits, it must be handled with care:
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Toxicity: High levels of tellurium exposure can cause health issues.
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Environmental impact: Improper disposal of tellurium compounds can harm aquatic and soil environments.
Industries that use tellurium must follow strict guidelines to ensure safety and sustainability.
Quick Recap of Tellurium’s Oxidation States
| Oxidation Number | Common Form | Example Compound |
|---|---|---|
| -2 | Telluride ion | Sodium telluride (Na₂Te) |
| +2 | Low-valent compounds | Tellurium dichloride (TeCl₂) |
| +4 | Oxide and similar forms | Tellurium dioxide (TeO₂) |
| +6 | Highly oxidized compounds | Telluric acid (H₆TeO₆) |
The oxidation number of tellurium varies depending on the compound, most commonly appearing as -2, +2, +4, and +6. Understanding these oxidation states is key to predicting how tellurium behaves in chemical reactions, industrial processes, and even environmental cycles. From strengthening metals to enabling solar power, tellurium’s oxidation numbers unlock a world of possibilities. Whether you are a student, hobbyist, or industry professional, having a clear understanding of tellurium’s chemical behavior helps connect complex science to practical applications.