Answer: 1) The element that would be the most effective at accepting electrons from another reagent is Cl.
2) The element that would be expected to be the best insulator is Cl (non-metal).
3) The element that is best able to form an ionic compound with sulfur is Rb.
Explanation:
Metals are the species which readily lose electrons in order to attain stability and non-metals are the species which readily accept an electron in order to attain stability.
Generally, metals on combining with non-metals lead to the formation of an ionic compound. For example, is an ionic compound where Rb is the metal and S is the non-metal.
Out of the given option Cl is highly electronegative in nature so it will readily accept an electron from a donor atom.
Insulator are the substances which do not allow electric current to pass through them. For example, non-metals are insulators.
Thus, we can match the elements below to the appropriate blanks in the following sentences.
1) The element that would be the most effective at accepting electrons from another reagent is Cl.
2) The element that would be expected to be the best insulator is Cl (non-metal).
3) The element that is best able to form an ionic compound with sulfur is Rb.