9.
The atomic number of an element is the total number of which particles in the nucleus?
a. electrons
protons and electrons
neutrons
d. protons

D - it is the number of protons in the nucleus

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.

every chemical equation adheres to the law of conservation of mass, which states that matter cannot be created or destroyed. therefore, there must be the same number of atoms of each element on each side of a chemical equation.