What are the terms that describe these values for the element oxygen?

18 = Mass umber

8 = atomic number

Explanation:

An atom is smallest unit of a matter or substance.It consist of three subatomic particles : electrons, protons, neutrons.

Protons and neutrons are located in the center of an atom where while mass of an atom is concentrated.

Mass number = Number of protons + Number of neutrons

Atomic number = Number of protons = Number of electrons (for a neutral atom)

General representation of an element is given as:

where,

Z represents Atomic number

A represents Mass number  

X represents the symbol of an element

Oxygen is the 8th element of the periodic table and is written as , thus 8 = atomic number and 18= Mass number

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.

the answers would be

the first one and the second one