Question

In january 2016, the discovery of four new elements was announced: 113, 115, 117, and 118. If these elements were stable enough for their properties to be studied, use your knowledge of the periodic table to predict some of the expected chemical and physical properties of these elements.

Answer 1

The last known element is Copernicium, Cn having atomic number 112. Therefore, Cn has 112 protons in the nucleus and 112 electrons in the electronic shells or sub-shells. The electronic configuration of Cn is given as

Cn: [Rn]5f¹⁴6d¹⁰7s².

The valence electrons in Cn occur in the 6d orbital which is the highest energy orbital available to Cn.

Let the four new elements be denoted as A, B, C and D.

A has atomic number 113, i.e, there are 113 electrons and 1 electron more than Cn. The extra electron will go in the 7p orbital, i.e, the electronic configuration of A is

A:[Rn]5f¹⁴6d¹⁰7s²7p¹.

Therefore, A will occur in Group 13 of the periodic table. A is expected to be a metal and have an inherent electron deficiency. Therefore, compounds of A are expected to dimerize easily.

B has atomic number 115, i.e, there are 115 electrons and 3 electrons more than Cn. The extra electrons will go in the 7p orbital, i.e, the electronic configuration of B is

B:[Rn]5f¹⁴6d¹⁰7s²7p³.

Therefore, B will occur in Group 15 of the periodic table. B is expected to be a metal. Since the outer orbital (7p) in B is half filled, B is expected to be highly stable and hence, less reactive.

C has atomic number 117, i.e, there are 117 electrons and 5 electrons more than Cn. The extra electrons will go in the 7p orbital, i.e, the electronic configuration of C is

C:[Rn]5f¹⁴6d¹⁰7s²7p⁵.

Therefore, C will occur in Group 17 of the periodic table. C is expected to be a non-metal; more specifically, a halogen. Since At is a solid halogen at room temperature, the next congener, i.e, C is expected to be a solid. C can easily form anions by accepting an electron from an electron-rich atom, i.e, C is expected to be highly reactive.

The next element D has atomic number 118. Thus, there are 118 electrons in D and the electronic configuration of D is

D: [Rn]5f¹⁴6d¹⁰7s²7p⁶

The outer shell (7p) is completely filled. Therefore, D must be a noble or inert gas and must be unreactive.