Introduction:
The oxygen family consists of elements in group 16 of the periodic table, including oxygen, sulfur, selenium, tellurium, and polonium. These elements exhibit similar chemical properties due to their valence electron configuration of six electrons in the outermost shell. The boiling and melting points of these elements decrease down the group.

Effect of Atomic Size:
The atomic size of the elements in the oxygen family increases down the group. This is due to the addition of new energy levels to the atom as we move down the group. The increase in atomic size leads to a decrease in the strength of the metallic bond between atoms. This results in a decrease in the boiling and melting points of the elements down the group.

Effect of Electronegativity:
The electronegativity of the elements in the oxygen family decreases down the group. Electronegativity is the tendency of an atom to attract electrons towards itself in a chemical bond. As we move down the group, the number of energy levels in the atom increases, leading to a decrease in the effective nuclear charge experienced by the valence electrons. This results in a decrease in the electronegativity of the elements down the group.

Effect of Bond Strength:
The strength of the chemical bond between atoms decreases down the group in the oxygen family. This is due to the decrease in the electronegativity and atomic size of the elements down the group. The weaker the bond strength, the easier it is for the atoms to break apart and move away from each other. This results in a decrease in the boiling and melting points of the elements down the group.

Conclusion:
In conclusion, the boiling and melting points of the elements in the oxygen family decrease down the group due to the increase in atomic size, decrease in electronegativity, and decrease in bond strength. These trends can be observed in other groups of the periodic table as well and are important to understand when studying the properties of elements.

The atomic size increases from oxygen to tellurium, the melting and boiling points also increase. The huge distinction between the melting and boiling points of oxygen and sulfur might be clarified on the premise that oxygen exists as a diatomic atom while sulfur exists as a polyatomic particle.