Question

The chemical formula for zinc oxide is $\mathrm{ZnO}$. Predict the formulas for each of the following similar compounds: (a) cadmium oxide (b) cadmium sulfide (c) cadmium selenide (d) cadmium telluride

Short answer

(a) CdO, (b) CdS, (c) CdSe, (d) CdTe

Step-by-step solution

Identify the elements

Zinc oxide is made up of zinc (Zn) and oxygen (O). To predict similar compounds for cadmium, we identify the cadmium (Cd) as the similar element to zinc. For each compound, we'll use cadmium with other elements that occupy the group with oxygen in the periodic table.

Determine the charge of cadmium

Cadmium typically has a charge of +2, similar to zinc, when forming compounds. This charge will help us determine the neutral formula for each cadmium-containing compound.

Predict the formula for cadmium oxide

The most common oxidation state for oxygen in compounds is -2. With cadmium having a charge of +2, the compound with oxygen is cadmium oxide, which is represented as $(\mathrm{CdO})$. Oxygen's -2 charge balances cadmium's +2 charge.

Predict the formula for cadmium sulfide

Sulfur, in the same group as oxygen, typically has a charge of -2. This makes the formula for cadmium sulfide $\mathrm{CdS}$, as cadmium's +2 charge balances sulfur's -2 charge.

Predict the formula for cadmium selenide

Selenium, also in the same group as oxygen, typically has a charge of -2. Thus, the formula for cadmium selenide is $\mathrm{CdSe}$, since cadmium's +2 charge balances selenium's -2 charge.

Predict the formula for cadmium telluride

Tellurium, following the same pattern as other group members, typically has a charge of -2. The formula for cadmium telluride is $\mathrm{CdTe}$, with cadmium's +2 charge balancing tellurium's -2 charge.

Key concepts

Zinc Oxide

Zinc oxide is a chemical compound that consists of zinc and oxygen elements. Its molecular formula is $\mathrm{ZnO}$.
This compound is widely used across different industries due to its versatility and excellent properties.
In the periodic table, zinc is a transition metal, usually found in the d-block and known to form a +2 oxidation state.
Oxygen, on the other hand, is in group 16, also known as the chalcogens, which typically exhibit a -2 oxidation state in compounds.

This combination results in a neutral compound, because the charges of zinc and oxygen balance each other out perfectly:

• Zinc’s +2 charge
• Oxygen’s -2 charge

These charges neutralize to form the stable compound zinc oxide, a result of the complete transfer of electrons between zinc and oxygen.
The compound is commonly used in various products like sunscreens, paints, and rubber due to its protective and durable properties.

Cadmium Compounds

Cadmium compounds, similar to zinc compounds, are often formed with elements from group 16 of the periodic table.
Just like zinc, cadmium typically has a +2 oxidation state when forming compounds. This entails that cadmium lends electrons to elements that accept electrons, such as those in the chalcogen group.

When combined with elements from group 16, we get stable cadmium compounds:

• Cadmium oxide $\mathrm{CdO}$
• Cadmium sulfide $\mathrm{CdS}$
• Cadmium selenide $\mathrm{CdSe}$
• Cadmium telluride $\mathrm{CdTe}$

These compounds form when cadmium's +2 charge precisely counteracts the -2 charge of the oxygen, sulfur, selenium, or tellurium.
Cadmium compounds are important in semiconductors and photovoltaic cells due to their unique electrical properties.
In sum, the consistency in charge balance across these compounds shows a remarkable property of metals like cadmium and zinc in forming stable binary compounds with nonmetals.

Periodic Table Groups

The periodic table is organized into columns called groups, where elements with similar properties are arranged together. Group 16 of the periodic table includes elements like oxygen, sulfur, selenium, and tellurium.
These elements are also known as chalcogens and share the characteristic of typically having a -2 oxidation state in compounds.

The properties of these elements are crucial for understanding how they form compounds with metals like zinc and cadmium.

• Group 16 elements are essential in forming various metal compounds
• Chalcogens readily accept electrons due to their high electronegativity
• They form stable compounds with metals that have a +2 oxidation state

For instance, in the case of zinc oxide $\mathrm{ZnO}$ and cadmium compounds like $\mathrm{CdS}$, $\mathrm{CdSe}$, and $\mathrm{CdTe}$, elements from group 16 play a critical role.
By accepting electrons from metals, these elements complete their electron shells, leading to stable, ionic compounds that are prevalent in both nature and industrial applications.