Two elements, P and Q, have the following configurations:
P: 2, 8, 5 Q: 2, 8, 7
(A) Which element is more reactive?
(B) Will P and Q form ionic or covalent bonds when they combine?
Explain using electron transfer or sharing.
(C) Predict the formula of the compound they would form.
Element P has the electronic configuration 2, 8, 5, so it has 5 valence electrons.
Element Q has the electronic configuration 2, 8, 7, so it has 7 valence electrons.
(A) Element Q is more reactive because it needs only one electron to complete its octet and attain a stable electronic configuration.
(B) P and Q will form a covalent bond because both are non-metals and both need to gain electrons to achieve stable configuration. Therefore, they achieve octet by sharing electrons. Element P needs 3 electrons to complete its octet, while each atom of Q needs 1 electron. Hence, one atom of P shares electrons with three atoms of Q.
(C) The valency of P is 3 and valency of Q is 1. So, the formula of compound after criss-cross method will be PQ.
