Answer: Im not sure if you are doing this in your class.
Explanation:
So... for the element of MAGNESIUM, you already know that the atomic number tells you the number of electrons. That means there are 12 electrons in a magnesium atom. Looking at the picture, you can see there are two electrons in shell one, eight in shell two, and two more in shell three
A chemical reaction must occur for a compound to have different properties.
Answer:
Ammonia is the richest source of nitrogen on a mass percentage basis because it has 82.35% of nitrogen by mass.
Explanation:
Percentage of element in compound :

(a) Urea, 
Molar mass of urea = 60 g/mol
Atomic mass of nitrogen = 14 g/mol
Number of nitrogen atoms = 2

(b) Ammonium nitrate, 
Molar mass of ammonium nitrate = 80 g/mol
Atomic mass of nitrogen = 14 g/mol
Number of nitrogen atoms = 2

(c) Nitric oxide, NO
Molar mass of nitric oxide = 30 g/mol
Atomic mass of nitrogen = 14 g/mol
Number of nitrogen atoms = 1

(d) Ammonia, 
Molar mass of ammona = 17 g/mol
Atomic mass of nitrogen = 14 g/mol
Number of nitrogen atoms = 1
Ammonia is the richest source of nitrogen on a mass percentage basis because it has 82.35% of nitrogen by mass.
Answer:
sedimentary rock
Explanation:
Because there are three stages, first igneous rock changes into either sedimentary rock or meatamorphic rock.