What are the principal energy level? And what do they represent?

the principal energy level of an electron refers to the shell or orbital in which the electron is located relative to the atoms nucleus. the first element in a period of the periodic table introduces a new principal energy level.

Explanation:

the electrons surrounding an atom are located in region around the nucleus called "energy level".

the answer is: they rebelled against saddam hussein’s rule.

kurds opposed saddam rule and wanted independence. kurds in the north and shiites in the south revolt against hussein.

for example, the halabja attack in 1988 conducted against the kurdish people by the iraqi regime under saddam hussein, where between 4000 people are killed and around 9000 are injured.