An unkown element has been found to occur in two different stable isotopes. One isotope has an abundance of 57.21 percent and has a mass of 120.9 amu. The other isotope has an abundance of 42.79 percent and has a mass of 122.9 amu. What is the average atomic mass of the unknown element?

121.7558 amu

Explanation:

Average atomic mass of the unknown element =

(Mass of isotope 1 x Relative Abundance of Isotope 1) + ( Mass of Isotope 2 x Relative Abundance of Isotope 2)

(120.9 x 0.5721) + (122.9 x 0.4279) = 69.16689 + 52.58891

Average mass of the unknown element = 121.7558 amu

intermolecular forces are the forces between molecules or particles.

there are two kinds of van der waals forces: weak london dispersion forces and stronger dipole-dipole forces.

in molecule of water there are dipole-dipole forces between negatively charged oxygen from one molecule of water and positively charger hydrogen of another molecule of water.

hydrogen bond is an electrostatic attraction between two polar groups that occurs when a hydrogen atom (h), covalently bound to a highly electronegative atom such as flourine (f), oxygen (o) and nitrogen (n) atoms.