Question

An element a has valency +3 while another element b has valency-2 give the formula of their compound formed when A reacts with B

Answer 1

when A reacts with B,
the chemical formula of their combination reaction would be A2B3.
For eg: Aluminium (+3)
Oxygen (-2)
Al+ O2---> Al2O3

Answer 2

The formula of the compound formed when A reacts with B is A2B3.

• The number of valence electrons in A is 3. So the A atom loses its 3 valence electrons to form a tripositive cation, that is, A^+3, to attain a stable configuration.
• Similarly, the number of valence electrons in B is 6. So the B atom gains its 2 more electrons to form a dinegative anion, that is, B^-2, to attain a stable configuration.
• Chemically, two reacting ionic species react together to balance their individual charges to form a neutral compound.
• If 2 ions of A react with 3 ions of B, their combined charges get balanced to 0 and firm a stable molecule, A2B3.
• That's why A2B3 is the correct answer to this question.