Chemistry - Covalent Bonding

The [blank_start]electrostatic[blank_end] attraction force between the [blank_start]positive[blank_end] nucleus and [blank_start]negative[blank_end] shared pair of electron.

Which of the following molecules is NOT formed by covalent bonding?

Simple Covalent Molecule: - Contains a [blank_start]few[blank_end] atoms. - Generally [blank_start]liquid[blank_end] and gas at room temperature, but if [blank_start]solid[blank_end] brittle in nature. - have [blank_start]weaker[blank_end] van der waal force between molecules. - have low melting point and [blank_start]boiling point[blank_end]. - do not dissolve in [blank_start]water[blank_end] but inorganic solvent. - do not conduct [blank_start]electricity[blank_end].

Covalent (Simple) Molecules have a low melting point and boiling point. - Simple covalent molecules have [blank_start]strong[blank_end] covalent bond within the atoms. - However, they have [blank_start]weaker[blank_end] inter-molecular attraction force, known a Van der Waal force. - So it requires [blank_start]small[blank_end] energy to break the attraction force. Covalent molecules do not dissolve in water. - Covalent molecules are mostly [blank_start]non-polar[blank_end]. Water is a [blank_start]polar compound[blank_end]. - Non-polar molecules like H2, Cl2, N2 and CH4 will [blank_start]not be dissolved[blank_end]. - However some molecules like HCl, NH [blank_start]will be dissolved[blank_end].