Final answer:
The ratio of beryllium (Be²+) to chlorine (Cl⁻) in the compound they form is 1:2, based on their electron configurations and the need to achieve charge neutrality in the resulting compound. Therefore correct option is B
Step-by-step explanation:
Based on the electron configuration of beryllium and chlorine, we can predict the ratio of metal cation to nonmetal anion in the compound they form.
Beryllium has an electron configuration of 1s²2s², with 2 electrons in its outer shell. Beryllium tends to lose these two electrons to form a Be²+ cation with a noble gas configuration, similar to helium.
Chlorine has an electron configuration of 1s²2s²2p⁶3s²3p⁵ and has 7 electrons in its outer shell. It tends to gain one electron to reach the noble gas configuration of argon, forming a Cl⁻ anion.
To maintain electrical neutrality, one Be²+ cation will combine with two Cl⁻ anions, resulting in the formula BeCl₂. Therefore, the ratio of beryllium to chlorine in the compound is 1:2, which corresponds to option B.