Answer:
1 : 2
Explanations
Given the following electronic configuration for the following elements
Beryllium 1s²s²
Chlorine 1s²2s²2p⁶3s²3p⁵
For the beryllium metal, the element has 2 valence electrons in its outermost shell (2s²) and loses these valence electrons to form a Be2+ cation. This shows that the element has a charge of +2 (cationic atom)
Similarly, for the element chlorine, the element has 7 electrons in its outermost shell (3s²3p⁵). The element gain needs 1 electron to complete its shell. Hence it gains an electron from another element to form an anion (Cl-). This shows that the chlorine element has a charge of -1
Hence the ratio of metal cationic (+) atom to nonmetal anionic (-) atom in the compound is 1 to 2.