Why would fluorine have such a high ionization energy compared with the ionization energy of barium?

Ionization energy is a measure of how much energy you need to input in order to remove an electron from an atom's outer shell.  This becomes easier for atoms that have less valence electron because it brings them closer to having a full out shell by shaving off the one or two extras they have.  However, this is harder for atoms that have near full valence electrons since they only need one or two additional electrons to become stable.  Fluorine has 7 electrons in its valence shell, so it wants to gain rather than subtract electrons to reach an octet.  Barium, on the other hand, has way less and will give up electrons much more 'willingly'.  Thus, since it is harder, it takes more energy to remove electrons from fluorine than barium.

out of these options:

ability to burn paper

pure sodium reacting violently with water

the boiling point of water

helium does not tend to react with anything

i would say this is a physical property:

helium does not tend to react with anything

why? :

i said helium does not tend to react with anything because well, it reacts to ! but ability to burn paper, pure sodium reacting violently with water, & the boiling point of water are chemical or

physical properties: the properties of a substance that can be observed without changing the chemical makeup of the substance

chemical properties: properties of a substance relating to the chemical nature and reactivity of the substance