The percent by volume of a solution : 19.23%
<h3>Further explanation</h3>
Given
50 ml of ethanol
210 ml of water
Required
The percent by volume of a solution
Solution
Percent Volume (% v/v) : volume (ml) of solute/100 ml of solution ⇒ ratio of the volume of the solute to total volume of the solution

solute= Ethanol
solvent=water
Solution = solute+solvent
Total volume of the solution :

Percent by volume :

The answer is a graduated cylinder
<h3><u>Answer;</u></h3>
As, & Sr --------[Kr]
Be ------------------- [He]
O, & Mg ----------[Ne]
S, & Ca -------------[Ar]
<h3><u>Explanation</u></h3>
- <u>The Be+ ion has 2 electrons, just like He. The ions Mg2+ and O2− each has 10 electrons like Ne. </u>
- <u>The S2− and Ca2+ each has 18 electrons like Ar. The ions As3− and Sr+ each have 36 electrons like Kr.</u>
- <u>Atoms of elements lose or gain electrons to attain a stable configuration which is equivalent to the configuration of noble gases.</u>
- When atoms lose or gain electrons they form ions, which are either positively charged or negatively charged. When atoms lose electrons they form positively charged ions while if they gain electrons the form negatively charged ions