A stable isotope has just<em> the right number of neutrons for the number of protons </em>(the <em>n:p ratio</em>) to hold the nucleus together against the repulsions of the protons.
A radioactive isotope has either too few or too many neutrons for the nucleus to be stable,
The nucleus will then emit <em>alpha, beta, or gamma radiation</em> in an attempt to become more stable.
I believe it will be A. Density, temperature, and viscosity, can be found in water through tests. Hope this helps! Mark as brainly please!
1 mole of any gas under STP ----- 22.4 L
18.65 L*1 mol/22.4 L ≈ 0.8326 mol N2