The literature values listed for the unknowns in this assignment are from either the Merck Index or the CRC Handbook, the two most used reference handbooks. However, the values tend to vary slightly across literature sources and sometimes the temperatures are given as ranges. Give at least one reason for the variations in these reported temperatures. In general, the boiling points of compounds increase down a group in the periodic table. The melting points and boiling points for the hydrogen compounds of group 6A elements are in the table below.

Melting Point (°C) Boiling Point (°C)
H2O 0 100
H2S –82.0 –60.0
H2Se –65.7 –41.2
H2Te –49.0 –2.2

Use your understanding of chemistry to propose an explanation for the anomaly in the trend for the hydrogen compounds of group 6A elements shown in the table above.