What is meant by noble gas envy?

Answer 1

Noble gas envy is a fun term used to explain how all the elements on the Periodic Table want to "look like" the Noble gases. Why? Because noble gases have an outer electron configuration of s2p6 - their outer s and P subshells are full with 8 electrons. This is a stable state. The other elements will either lose, gain or share electrons with other elements to attain 8 outer electrons. Example element 9 is fluorine with 9 total electrons, but it's outer shell only has 7. It will gain an extra electron to "look like" Neon, which has 8 outer electrons. Fluorine is still fluorine, but now it has a -1 charge and is a fluorine ion. Metal elements will lose electrons until they have only 8 outer shell electron and become positively charged.

Answer 2

This refers to the fact that many atoms will tend to gain or lose electrons to mimic the electron configurations of noble gasses.