The correct answer is: _________________________________________________________ " F and Br , because they are in the same group" . _________________________________________________________ Note: _________________________________________________________ Choice [B]: "F and Br ; because they are in the same period" ; is incorrect; since "F" and "Br" are not in the same "period" (that is, "row"). ______________________________________________________ Choice [C]: "Na and Mg; because they are in the same group {"column"} ; is incorrect; since: "Na" and "Mg are NOT in the same group {"column"]. _______________________________________________________ Choice [D]: "Na and Mg" ; because they are in the same period {"row"}; is incorrect. Note: "Na" and "Mg" are, in fact, in the same period {"row"}. However, as aforementioned, {Mg and Na} are not in the same group {"column".}.
Note: The similiarities in physical and chemistry properties among elements are determined and organized — or tend to be so—by "groups" {"columns"} — NOT by "periods" {rows}. ______________________________________________________
