A). 4
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Answer:
Ionization energy increases going left to right across a period and increases from bottom to top in a group
Electron affinity increases when going up a group
If we are excluding noble gases (aka group 8/18), Chlorine is the element that has the greatest electron affinity. This is because Fluorine's 2p orbital is limited and packed which doesn't quite allow sharing of the orbital with extra electrons easily, while Chlorine has a 3p orbital allowing more space for electrons, where the orbital electrons would be inclined to do so.
Helium is the element with the greatest ionization energy since it's at the top and energy (from Oganesson to Helium) increases when going across a period (from Hydrogen to Helium).
The structure is known as the nucleus
