From the following list of elements—Ar, H, Ga, Al, Ca, Br, Ge, K, O—pick the one that best fits each description. Use each element only once: (a) an alkali metal. (b) an alkaline earth metal. (c) a noble gas. (d) a halogen. (e) a metalloid. (f) a nonmetal listed in group 1A. (g) a metal that forms a 3+ ion. (h) a nonmetal that forms a 2-ion. (i) an element that resembles aluminum.
Solution : Here, we have to identify the element that fits the description among the given elements. Step 1: (a) an alkali metal - Among the given elements - K(Potassium) belongs to group 1A. Group IA elements are called as alkali metals and they are very reactive metals that do not occur freely in nature. Hence K is an alkali metal. (b) an alkaline earth metal - Among the given elements - Ca(Calcium) belongs to group 2A. Group 2A elements are called as Alkaline earth metals. Hence C a is an alkaline earth metal. (c) a noble gas - The elements that belong to group 8A that are in the extreme right of the periodic table are called as noble gases and they are inert in nature which means they do not take part in chemical reactions. Among the given elements - Ar(Argon) belongs to group 8A and is a noble gas. (d) a halogen - Group 7A elements are called as halogen elements. Among the given elements, Br(Bromine) belongs to group 7A and is halogen element. The halogens are diatomic meaning they exist as molecules, each with a pair of atoms. Ex : bromine molecular formula is Br . 2 (e) a metalloid - Metalloids are chemical elements that have properties common with both metals and nonmetals. These elements are found along the step like line between metals and nonmetals of the periodic table. Among the given elements, Germanium(Ge) is a metalloid. (f) a nonmetal listed in group 1A - Element Hydrogen(H) belongs to group 1A and is the nonmetal in group 1A. (g) a metal that forms a 3+ ion - Among the given elements, Al(Aluminium) has charge of +3, which means it loses 3 electrons to achieve the nearest stable electron configuration forming 3+ ion. (h) a nonmetal that forms a 2-ion. Oxygen(O) among the given elements belongs to group 6 and gains 2 electrons to form 2- ion. (i) an element that resembles aluminum - Elements of the same group exhibits similar properties. Aluminium belongs to group 3A and among the given elements, ga(Gallium) belongs to group 3A and hence it resembles aluminium(Al).