Despite being an extremely rare gas on Earth, hydrogen is the most common element in the universe. This is due to the fact that hydrogen is the fuel for stars, as it undergoes the fusion nuclear reaction to form helium and release the energy to sustain the star. Therefore, the answer to this question is hydrogen.
Actually, to examine it physically, then you could use a physical property that shows it's appearance. To examine its bonds etc, you'd need a chemical property. So, False.
This problem is providing us with a statement in which we need to figure out the word fitting in the blank. At the end, after analyzing the information, the word turns out to be colligative as show below:
<h3>Colligative properties.</h3>
In chemistry, colligative properties of solutions account for the behavior of a solution with respect to the pure solvent, to which a solute is added.
Among them, we have boiling point elevation, freezing point depression, vapor pressure lowering and osmotic pressure, which are all affected by the concentration of the solute but not by the identity of the solute.
In such a way, we conclude that the correct word that fits in the blank is colligative as shown below:
"Colligative properties depend on the concentration of a solute in a solution but not on the identity of the solute."
Learn more about colligative properties: brainly.com/question/10323760
Ra-226 will go through α decay which means the nucleus of radium-226 will emit a α particle. α particle consists of 2 protons and 2 neutrons. So it will become Rn-222.
The answer would be D. Soluble means that it can be dissolved by water.