Question

What would you expect the combining ratio to be for alkali metals to be with a halogen? With oxygen?

Answer 1

The combining ratio for alkali metals and halogens is `1:1`.

The combining ratio for alkali metals and oxygen is `2:1`.

Explanation:

Alkali metals form `1^+` ions. Halogens form `1^-` ions. Oxygen forms `2^-` ions.

Ionic compounds are neutral, so the total positive charge has to equal the total negative charge.

Alkali metals plus halogens: potassium and chlorine

`"K"^+ + "Cl"^(-)` `rarr` `"KCl"`

The combining ratio for alkali metals and halogens is `1:1`.

Alkali metals plus oxygen: potassium and oxygen

`"2K"^+ + "O"^(-2)` `rarr` `"K"_2"O"`

The combining ratio for alkali metals and oxygen is `2:1`.

Answer 2

Alkali metals all have a single valence electron, and halogens have a single missing one, so they would combine in a 1:1 ratio.

Oxygen requires two more valence electrons to complete its shell, so it would combine in a 2:1 ratio.

Explanation:

Elements combine (react) to form more stable compounds based on their electronic structure – specifically the valence electrons.

Groups 1, 2, and 17 (halogens) have only one more stable configuration, and Group 16 have a primary configuration, but may also have additional ones. The “transition metals” have a variety of possible stable electronic configurations with other elements. https://www.webelements.com/