Chapter 11, Problem 73A

Interpretation Introduction

Interpretation: Chemical and Physical properties of an unknown element having atomic number 120 must be determined.

Concept introduction: Electron configuration of an atom shows the filling of electrons among the orbital shells and sub-shells. Physical and chemical properties of elements are related to their electron configurations. The valence electrons that is electrons in the outermost shell determines the chemistry of the element.

Explanation of Solution

Electronic configuration of unknown element having atomic number 120 is $[\text{Og}]8{\mathrm{s}}^2$ .

Oganesson (Og) atoms have 118 electrons and the shell structure is 2, 8, 18, 32, 32, 18.

Since, the outer electronic configuration is $\mathrm{n}{\mathrm{s}}^2$ the element expected to exhibit properties of alkaline earth metals.

Thus, the chemical and physical properties of this unknown element will resemble alkaline earth metals.

Physical properties

• Shiny and silver-white.
• Reactive at standard temperature and pressure.
• Low densities.
• low melting and boiling points

Chemical properties

• React with water to evolve hydrogen gas.
• Combine with halogen at high temperature forming their halides.
• Combine with hydrogen directly on heating to form metal hydride of general formula ${\text{MH}}_{\text{2}}$ .
• Reacts with acids to liberate hydrogen.