Use the quantitive chemistry formula triangle on google
Solid particles are all compacted together, liquid particles are not as close as solid particles but still move together, and gas particles do not stay together
An atomic number is the number of protons that the atom of a particular element has.
For example, take carbon. Carbon has 6 protons. It's atomic number is 6.
Answer:
is the isotopic notation of the atom
Explanation:
The isotope notation is:

<em>Where a is the mass number = Number of protons + Number of neutrons</em>
<em>b is atomic number = Number of protons</em>
The atomic number define the nature of the atom, the element with atomic number = 15 is phosphorus, P:

a = 15 protons + 16 neutrons = 31
b = 15
is the isotopic notation of the atom.