The molecule beryllium chloride has one beryllium atom, a metal, and two chlorine atoms, nonmetals. What kind of bond will they form?
Covalent
Beryllium chloride will form an ionic bond.
To determine the type of bond that will be formed between beryllium and chlorine atoms in beryllium chloride, we need to look at their electronegativities.
Electronegativity is a measure of an atom's ability to attract electrons towards itself in a chemical bond. The greater the difference in electronegativity between two atoms, the more polar the bond will be.
Beryllium, as a metal, has a relatively low electronegativity, while chlorine, as a nonmetal, has a relatively high electronegativity. The electronegativity difference is significant enough that the bond formed between beryllium and chlorine will be classified as ionic.
In an ionic bond, electrons are transferred from the metal (beryllium) to the nonmetal (chlorine). Beryllium will lose two electrons, forming a 2+ cation, and chlorine will gain one electron for each chlorine atom, forming 1- anions. The opposite charges of the ions will attract each other and form a strong electrostatic bond, resulting in the ionic compound beryllium chloride (BeCl2).
To summarize, beryllium chloride forms an ionic bond between the beryllium cation, which loses two electrons, and the chlorine anions, which each gain one electron.