Put the following elements in order of decreasing (from largest to smallest) atomic radius: Be, Ba, F, Ca.

 Ba, Ca, Be, F

Explanation:   Size of atom increases when moving down on same group

and decreases when moving on same period from left to right

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