na+F2-> naF a chemical reaction. the synthesis of sodium fluoride noF is shown above all chemical reactions involve a change to an atoms number of protons neutrons electrons

 Electrons

Explanation:

A chemical reaction usually only affects elctrons. A chemical reaction usually results in the electrons being transferred or shared. When sodium and fluorine react to produce sodium fluoride, a sodium electron is transferred to the fluorine to produce ionic bonds. This ionic bond exists between the sodium cation and fluoride (fluorine) anion.

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