Why do beryllium and flouine combine in a 1:2 ratio?

Be has two electrons to give away; F has 7 electrons and needs one; therefore, two F atoms are needed to take the two electrons from Be.

Beryllium and fluorine combine in a 1:2 ratio due to the principle of chemical stoichiometry. Stoichiometry describes the quantitative relationship between reactants and products in a chemical reaction.

To understand why beryllium and fluorine combine in a 1:2 ratio, we need to examine the electron configurations of these elements. Beryllium has an atomic number of 4, meaning it has four electrons. These electrons are distributed among the 1s and 2s orbitals.

On the other hand, fluorine has an atomic number of 9, with its electrons distributed among the 1s, 2s, and 2p orbitals. The outermost energy level of fluorine, the 2p level, is only one electron short of being fully occupied. Fluorine reacts readily to gain a single electron to complete its outer shell and achieve a stable electron configuration.

When beryllium and fluorine atoms react, beryllium loses its two valence electrons, leaving it with a stable electron configuration matching that of a helium atom. Fluorine gains one electron from each beryllium atom and achieves a stable electron configuration matching that of a neon atom. Each beryllium atom can donate two electrons, while each fluorine atom can accept one electron.

To achieve a balanced transfer of electrons, two fluorine atoms are required to react with each beryllium atom. This results in a 1:2 ratio between beryllium and fluorine in the compound, which is beryllium fluoride (BeF2).

To summarize, beryllium and fluorine combine in a 1:2 ratio because beryllium donates two electrons, while fluorine accepts one electron from each beryllium atom to achieve stable electron configurations. The principle of stoichiometry explains the ratio of elements involved in a chemical reaction.