I am only in 6th grade so all I have to say is good luck and I wish you the best on that quiz.
The characteristic bright-line spectrum of an element is produced when its electrons return to lower energy levels To be in the ground state all electrons must be in their lowest energy state; all excited atoms must lose energy. The lost energy appears in the form of light. Hope this helped :)
Answer:
The atomic radius of a chemical element is a measure of the size of its atoms, usually the mean or typical distance from the center of the nucleus to the boundary of the surrounding shells of electrons. ... The value of the radius may depend on the atom's state and context.
Explanation:
Answer:- Yes, strontum bromide and potassium sulfate gives a precipitate of strontium sulfate.
Explanations:- As per the solubility rules, all compounds of alkali metals are soluble.
Sulfate of most of the alkaline earth metals like Ca, Ba and Sr are insoluble.
A double displacement reaction takes place when strontium bromide and potassium sulfate are mixed and a precipitate of strontium sulfate is formed:

Note: (aq) stands for aqueous and (s) stands for solid and here it's precipitate.
C-12? (6 protons) C-13? (6 protons) C-14? (6 protons)