Question

An element forms an oxide, \(\mathrm{E}_{2} \mathrm{O}_{3},\) and a fluoride, \(\mathrm{EF}_{3}\) (a) Of which two groups might \(\mathrm{E}\) be a member? (b) How does the group to which E belongs affect the properties of the oxide and the fluoride?

Short answer

(a) Group 13 or Group 15 (b) Group 13 elements form amphoteric oxides and Lewis acid fluorides; Group 15 elements form acidic oxides and different Lewis acid fluorides.

Step-by-step solution

- Determine the oxidation state in the oxide

In the oxide \(\mathrm{E}_{2}\mathrm{O}_{3}\), \(E\) must balance the total oxidation state of \(O\). Oxygen generally has an oxidation state of \(-2\). Thus, for \(O_3 = 3 \times -2 = -6\). Since the formula indicates two \(E\) atoms and the compound is neutral, each \(E\) must have an oxidation state of \(+3\).

- Determine the oxidation state in the fluoride

In the fluoride \(\mathrm{EF}_{3}\), we must balance the total oxidation state of the fluorine atoms. Fluorine generally has an oxidation state of \(-1\). Thus, for \(3F = 3 \times -1 = -3\). Hence, the oxidation state of \(E\) is \(+3\), as the compound is neutral.

- Identify the possible groups

Elements that commonly form compounds with a \(+3\) oxidation state might belong to Group 13 (Aluminum group) or Group 15 (Nitrogen group) of the periodic table.

- Properties related to the group

If \(E\) is from Group 13: The oxide \(\mathrm{E}_{2}\mathrm{O}_{3}\) will likely be amphoteric (e.g., \(\mathrm{Al}_{2}\mathrm{O}_{3}\)). The fluoride \(\mathrm{EF}_{3}\) will generally be a Lewis acid. If \(E\) is from Group 15: The oxide \(\mathrm{E}_{2}\mathrm{O}_{3}\) will be more acidic (e.g., \(\mathrm{P}_{2}\mathrm{O}_{3}\)). The fluoride \(\mathrm{EF}_{3}\) could also act as a Lewis acid but with different reactivity and properties than those of Group 13 elements.

Key concepts

Periodic Table Groups

The periodic table is divided into groups and periods. Groups are the vertical columns, numbered from 1 to 18. Elements within the same group often have similar properties because they have the same number of valence electrons. In the context of the exercise, elements forming compounds with a +3 oxidation state are likely from Group 13 or Group 15.

• Group 13 elements, like Aluminum (Al), often form compounds with a +3 oxidation state.
• Group 15 elements, like Phosphorus (P), can also achieve a +3 oxidation state in some compounds.

Understanding the group helps in predicting the chemical behavior and properties of the element and its compounds.

Compound Formation

Compounds form when elements combine through chemical bonds. The type of bond and the element's oxidation state influence the resulting compound's properties. In our example:

• The oxide \(\text{E}_{2}\text{O}_{3}\) forms when two atoms of element E bond with three oxygen atoms.
• The fluoride \(\text{EF}_{3}\) forms when one atom of element E bonds with three fluorine atoms.

For these compounds, element E must balance the oxidation states to create a neutral compound. This balance helps in identifying the possible group and predicting compound properties.

Amphoteric Oxides

Amphoteric oxides are oxides that can react with both acids and bases. They are unique because they can exhibit both acidic and basic properties depending on the reaction conditions.

• Example: \(\text{Al}_{2}\text{O}_{3}\), from Group 13, is amphoteric.
• Amphoteric behavior: These oxides can neutralize acids (forming salts and water) and bases (also forming salts and water).

When an element like E is from Group 13, its oxide (\