Because in difrent materials atoms are more compact or less compact.if they are less compact then it will be easear for them to move
Answer to this is Radioactive isotopes.
Isotopes are the species of the same element having different atomic masses that means the number of protons remains the same but number of neutrons do differ. For example
and
are the two isotopes of Hydrogen (
).
Radioactive isotopes are the isotopes which release some kind of energy in the form of alpha particles, beta particles or gamma radiation. Examples of each of the decay processes are :
Alpha Decay: In this decay one alpha particle having atomic mass 4 and atomic number 2 or we can say a He molecule will come out. 
Beta Decay: In this decay a
particle is emitted increasing the atomic number of the reactant by 1 unit.

Gamma Radiation: In this type of reaction only radiation is emitted out which does not change the original molecule.

An ionic compound is a substance that contains atoms that are bonded together through an ionic bond, where electrons are transferred from one atom to another. For the given experiment above, the material that is missing from the list is WATER or solvent. It is necessary because conduction through water will help you identify if a sample compound is ionic through its electrolytes. <span>Ionic compounds that are soluble are typically electrolytes</span>
The correct option is C.
When glucose is stirred into water to form a solution, then glucose is the SOLUTE and water is the SOLVENT. A solute refers to a substance that is dissolved in a solvent. For instance, salt is the solute that is dissolved in salt solution. A solvent on the other hand refers to the liquid into which the solute was dissolved. For instance, in the case of salt solution, water is the solvent, because it is used to dissolve the salt.
Particles in a: gas are well separated with no regular arrangement. liquid are close together with no regular arrangement. solid are tightly packed, usually in a regular pattern.!