Answer :
Lithium and potassium are both alkali metals, which are found in Group I of the Periodic Table. These metals share certain properties because they belong to the same group.
Let's look at the characteristics of lithium and potassium:
- Lithium: It has a melting point of 181 °C and a density of 0.53 g/cm³.
- Potassium: We need to predict its melting point and density compared to lithium.
Alkali metals have the following general trend as you move down the group from lithium to potassium:
Melting Point: The melting points of alkali metals decrease as you move down the group. This means that potassium, which is below lithium in the group, will have a lower melting point than lithium.
Density: Typically, the density of alkali metals increases as you move down the group, but there are exceptions. Lithium is the least dense of the alkali metals, and while sodium, which is between lithium and potassium, has a higher density than lithium, potassium's density is actually lower than sodium’s and also lower than that of lithium.
Taking these trends into account:
- We expect potassium to have a melting point less than 181 °C.
- We expect potassium to have a density less than 0.53 g/cm³.
Thus, the correct choice is:
Option A: Melting point less than 181 °C and density less than 0.53 g/cm³.
