Answer:
Atomic number is the number of protons in an isotope or element.
Explanation: The atomic number is the same number of protons in an element or isotope and if said isotope is neutral than it is the same number of electrons.
Example: Atomic number = 19 Protons = 19 if neutral Electrons = 19
The equation that scientists could use to find the wavelength of the emission lines of the hydrogen atom would be that of Balmer.
The wavelength of the emission lines of the hydrogen atom can be derived using the Balmer series:
1/λ
Where λ = wavelength, = Rydberg constant, and n = level of the original orbital.
The equation becomes applicable in getting the wavelength of emitted light when electrons in hydrogen atoms transition from higher (n) orbital to lower orbital (2) levels.
More on the Balmer series can be found here: brainly.com/question/5295294
Solids - particles are very close together (highest density on the list)
Liquids - the particles slide past one another
Gases - particles bounce off of surroundings and the same particles of the gas