What determines the order of placement of the elements on the modern periodic table?
(1) atomic number(2) atomic mass(3) the number of neutrons, only(4) the number of neutrons and protons

The order of placement of the elements on the modern Periodic Table is the atomic number. The answer is number 1. The rest of the choices do not answer the question above. Atomic mass gives the number of mass of an atom. 

answer

the ions in solute supperate from eachouthere

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