There are three elements E, F, G with the atomic number 19, 8 and 17 respectively. Give the molecular formula of the compound formed between E and G.

Hint: So to approach this question one should know the electronic configuration of these elements. The electronic configuration helps us in determining how the electrons have been distributed in the orbitals. The valence electron of the electronic configuration helps in determining the chemical properties of the element such as valency. Here the valency will help in determining the molecular formula.

Complete step by step answer:
so let us first write the electronic configuration of these elements. So the electronic configuration for E is 2,8,1. This means the valency of the element is + 1 as the valence electrons is 1. So it needs to give its one electron to attain the noble gas configuration.
The electronic configuration for element F is 2,6. It should gain two electrons to attain noble gas configuration.
The electronic configuration for element G is 2,8,7. This has seven electrons in its valence shell but it needs only one electron to complete its octet so the valency is 1-.
So on observing we see that the element E and G has to give one electron and the other needs one electron respectively to attain noble gas configuration. So this means they will bond together by giving and taking one electron. So the molecular formula will be $${E_1}{G_1} = EG$$.

Note: The bond formed between EG will be an ionic or electrovalent bond. This is because of the large electronegativity difference between the two elements. The element E is electropositive and the element G is electronegative. So the bond formed has a high electronegativity difference.