How many electrons will magnesium have

12 electrons

Explanation:

MAGNESIUM, you already know that the atomic number tells you the number of electrons. That means there are 12 electrons in a magnesium atom. There are two electrons in shell one, eight in shell two, and two more in shell three.

in scientific notation, the value of the  speed of light in a vacuum

  will be written as 2.995 * 10^8. when this value is represented in the form of

  a * 10^b, then, a = 2.995 and b = 8.

the value of the speed of light in a vacuum given above can also be rounded up to approximately 300000000. in this case, the scientific notation will be written as 3 *10^8.

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.