Formula of the Compound Formed when Elements Combine with Oxygen

To determine the formula of the compound formed when an element combines with oxygen, we need to consider the valency of each element and the principle of charge balance.

Valency of Elements:
- Element A has a valency of 3.
- Element B has a valency of 1.

Combining with Oxygen:
When an element combines with oxygen, it forms an oxide. The valency of oxygen is typically 2.

Charge Balance:
To form a stable compound, the total positive charge of the cations (positively charged ions) should be equal to the total negative charge of the anions (negatively charged ions). In other words, the charges must balance.

Formation of Compound:
To determine the formula of the compound formed when elements A and B combine with oxygen, we need to find the ratio in which they combine to achieve charge balance.

Let's consider the following scenarios:

1. Element A combining with Oxygen:
- Valency of A = 3
- Valency of Oxygen = 2

To achieve charge balance, 2 atoms of element A will combine with 3 atoms of oxygen. This results in the formula A2O3.

2. Element B combining with Oxygen:
- Valency of B = 1
- Valency of Oxygen = 2

To achieve charge balance, 1 atom of element B will combine with 2 atoms of oxygen. This results in the formula BO2.

Therefore, the formula of the compound formed when element A combines with oxygen is A2O3, and the formula of the compound formed when element B combines with oxygen is BO2.

Summary:
- When element A with a valency of 3 combines with oxygen, it forms A2O3.
- When element B with a valency of 1 combines with oxygen, it forms BO2.

Note: The actual elements represented by A and B are not mentioned in the question, so specific examples cannot be provided. However, this explanation applies to any element with a valency of 3 and another element with a valency of 1 combining with oxygen.