<u>Answer:</u> The correct answer is the mass number of the most common isotope of the element is 24.
<u>Explanation:</u>
We are given:
An element having atomic number 12 is magnesium and atomic mass of the element is 24.305
The image corresponding will be 
The number '24.305' is the average atomic mass of magnesium element.
Average atomic mass is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.
Formula used to calculate average atomic mass follows:

Average atomic mass of magnesium = 24.305 amu
As, the average atomic mass of magnesium lies closer to the mass of Mg-24 isotope. This means that the relative abundance of this isotope is the highest of all the other isotopes.
The 'Mg-24' isotope is the most common isotope of the given element.
Hence, the correct answer is the mass number of the most common isotope of the element is 24.
Answer:
B
Explanation:
If the student needs one gram but so far only has 0.37 grams, then the amount they need is the difference between what they need and how much they already have. 1-0.37=0.63 grams.
...which isn't actually an option because none of them have decimal points but I would say it is B anyway because it is the equivalent ratio and maybe there was a typo.
Hope this helped!
Answer:
Compound B and D
Explanation:
Both are good conductors of electricity.
Answer:
The outer core of the earth is liquid.
Explanation:
Seismic waves travel through the Earth at different speeds and are reflected and refracted diffracted differently as they encounter layers of different densities.
By analyzing these waves, they have concluded that there is an inner core of solid iron surrounded by a liquid outer core consisting of nickel and iron.
A is wrong. The Earth consists of several layers
C is wrong. Seafloor spreading is caused by the movement of tectonic plates away from each other.
D is wrong. The mantle is mostly solid rock.
<span>Ionic compounds are chemical compounds in which ions are held together in a lattice structure by ionic bonds. They have a high melting and boiling point, and they have a high hardness and are very brittle. The cations and anions are stuck together in a sense. So in this case, sodium (Na) is attracted to Chlorine (Cl).</span>