Question

(1)The element potassium is less reactive than which of the following elements?

a. hydrogen b. lithium c. sodium d. cesium

(2)In which of the “Trends of the Periodic Table” is hydrogen the highest (or biggest) and iodine is the lowest (or smallest)?
a. ionization potential b. metallic character c. electron affinity d. ion size e. none of these

(3)

Which of the following ionic compounds would have the highest lattice energy?

a. KF b. KI c. MgO d. MgS e. AlP

Answer 1

1) hydrogen, lithium, sodium and cesium belongs to group IA of the periodic table. These elements are called as alkali earth metals. All these metals contains one elestron in their outer most orbital and by losing one electron they attain their nearest inert gas configuration, that is why alkali metals are highly reactive. It is a general characteristics of the alkali metals that with the increase in atomic size (down the group atomic size increases) the reactivity of the alkali metal increases. potassium belongs to 4th period, sodium belongs to 3rd period, hydrogen belongs to 1st period, lithium belongs to 2nd period and cesium belongs to 6th period of periodic table. As a result of which, cesium being in the 6th period and potassium in 4th period atomic size of Cesium is more than potassium and hence, potassium is less reactive than Cesium .