Question

Depending upon reaction conditions, phosphorus and sulfur can produce either \(\mathrm{P}_{2} \mathrm{~S}_{3}\) and \(\mathrm{P}_{2} \mathrm{~S}_{5} .\) Predict two formulas for each of the following compounds: (a) arsenic sulfide (b) antimony sulfide

Short answer

(a) \(\mathrm{As}_2 \mathrm{S}_3\), \(\mathrm{As}_2 \mathrm{S}_5\); (b) \(\mathrm{Sb}_2 \mathrm{S}_3\), \(\mathrm{Sb}_2 \mathrm{S}_5\).

Step-by-step solution

Understand the Problem

We are given two compounds formed by phosphorus and sulfur: \(\mathrm{P}_2 \mathrm{S}_3\) and \(\mathrm{P}_2 \mathrm{S}_5\). Our task is to predict similar compounds for arsenic and antimony, given their similarities with phosphorus in terms of group and valency.

Predict Arsenic Compounds

Arsenic is in the same group as phosphorus and can form similar compounds. Replace phosphorus with arsenic for both sulfur compounds. The predicted arsenic sulfide formulas are \(\mathrm{As}_2 \mathrm{S}_3\) and \(\mathrm{As}_2 \mathrm{S}_5\).

Predict Antimony Compounds

Antimony is also in the same group as phosphorus and arsenic, suggesting similar chemistry. Therefore, substitute phosphorus in the sulfide compounds with antimony. The predicted antimony sulfide formulas are \(\mathrm{Sb}_2 \mathrm{S}_3\) and \(\mathrm{Sb}_2 \mathrm{S}_5\).

Key concepts

Group Elements

Elements in the periodic table are organized into groups, which are columns that share certain properties. Group elements are particularly useful because they often display similar chemical behaviors. This happens because elements in the same group have the same number of electrons in their outer shell, known as valence electrons. These electrons are crucial as they determine how an element will react with others. Phosphorus, arsenic, and antimony are all part of Group 15. Due to this shared group membership, they exhibit similar reactive patterns and can often form analogous compounds when reacting with other elements like sulfur. Understanding group elements makes it easier to predict how unfamiliar elements might behave based on their position in the periodic table.

Valency

Valency refers to the ability of an atom to combine with other atoms, indicated by the number of bonds it can form. In simple terms, it tells us how many electrons an atom needs to lose, gain, or share to fill its outermost shell, or to achieve a stable electron arrangement.For phosphorus, arsenic, and antimony, their valency is typically 3 or 5. This means that they can form either three or five bonds with other elements. The compounds

• \( \mathrm{P}_2 \mathrm{S}_3 \) and \( \mathrm{P}_2 \mathrm{S}_5 \),
• \( \mathrm{As}_2 \mathrm{S}_3 \) and \( \mathrm{As}_2 \mathrm{S}_5 \),
• as well as \( \mathrm{Sb}_2 \mathrm{S}_3 \) and \( \mathrm{Sb}_2 \mathrm{S}_5 \),

are perfect examples of their valency in action. The ability to predict valency helps in understanding what kind of bonds a particular element can form, and thus aids in predicting chemical compounds.

Compounds Prediction

Predicting chemical compounds involves using known chemical properties of elements to foresee the types of molecules they will form. This process is simplified when we know the valency and group of the elements involved. Chemical formulas like \( \mathrm{P}_2 \mathrm{S}_3 \) and \( \mathrm{P}_2 \mathrm{S}_5 \) guide the prediction of similar compounds for Group 15 elements such as arsenic and antimony.When predicting compounds:

• First, identify the group and valency of the elements. Elements in the same group, like phosphorus, arsenic, and antimony, are likely to form similar compounds due to shared valency.
• Next, use the chemical formulas of known compounds as templates. Replace one element with another from the same group, keeping the valence and the balance of the formula intact.
• This method was used in predicting \( \mathrm{As}_2 \mathrm{S}_3 \) and \( \mathrm{As}_2 \mathrm{S}_5 \) for arsenic, and \( \mathrm{Sb}_2 \mathrm{S}_3 \) and \( \mathrm{Sb}_2 \mathrm{S}_5 \) for antimony from the phosphorus-sulfur compounds.

Understanding how to predict compounds can greatly aid in chemical synthesis and in anticipating new chemical behaviors.