Question

What will be the atomic number of the next alkali metal to be discovered? How would you expect the physical properties of the next alkali metal to compare with the properties of the other alkali metals summarized in Table?

Short answer

In contrast with the periodic table, the next alkali metal to be discovered will have an atomic number 119 with the properties of smaller ionization energy, a negative reduction potential, a larger${\text{M}}^{\text{+}}$ radius, and a lower melting point.

Step-by-step solution

Alkali metal Definition

Any element in the Group of the periodic table is classified as an alkali metal (the first column). Alkali metals are chemical entities that quickly lose one valence electron to create ionic compounds with non-metals. The alkali metal group includes all elements found in nature.

Atomic number of next alkali metal to be discovered

The alkali metals present in the periodic table are Lithium, Sodium, Potassium, Rubidium, Caesium, Francium having atomic numbers$\text{3,11,19,37,55,87}$ respectively.

So, according to the periodic table, the next alkali metal will be atomic number 119.

Properties of the next alkali metal to be discovered

According to table 18.4, the next alkali metal will have smaller ionization energy, a negative reduction potential, a larger${\text{M}}^{\text{+}}$ radius, and a lower melting point than the alkali metals above it in the periodic table.

Therefore, the next alkali metal will have atomic number 119 with properties such as small ionization and lower melting point.