Hydrogen and helium because they only have one electron shell and it only holds up to two electrons in it.
Answer:
1. Density can be used to identify a substance
2. Density can be used to ascertain whether a substance will float in water.
Explanation:
The calculation of the density of a substance can be used to identify the substance. If the density of a substance is calculated accurately, and compared with a table of standard densities, then we can identify that substance.
Also, density determines whether an object will float or sink in water. If an object is less dense than water then it will float in water. If it is denser than water, then it will sink in water.

It represents
<h2>A) 1,000 grams</h2>
(1 kilogram = 1000 grams)

Answer:
The Answer is gonna be C) high pressure and low temperature
The correct answer is B. Solubility describes the amount of solute that can be dissolved in a solvent. This value is not constant is affected by many factors. One factor is the temperature. An increase in temperature, a corresponding change in solubility also can be observed. The increase leads to a decrease in the solubility and the opposite. A decrease is observed since gas molecules are now has enough energy to escape the liquid phase and go to the gas phase.