The number of protons in the nucleus determines the atomic number of an element.
Every element has its own characteristic atomic number.
Answer:
The Atomic Number
Explanation:
The X would be the Atomic Number or amount of protons sorrounding the nucleus of that atom.
Sodium Flouride
Magnesium Nitrate
Calcium Phosphate
Sodium Oxide
Lead Iodide
Copper Sulphate
I've answered another one of your questions with the content of how to work these out
Answer:
net force is 80n ‐40n=40newton
the direction of motion is right