Answer: 55
Explanation: A atom consists of a nucleus and electrons.Nucleus contain neutrons with no charge and protons with positive charge. The electrons bearing negative charge revolve around the nucleus.
An electrically neutral atom contains equal number of protons and electrons. Thus if a neutral element X contains 55 protons, it also contains 55 electrons.
Answer:
an atom is the smallest particle of matter
a compound is a substance that has two or more atoms and element is the opposite of compound.
molecule is........,...............hope this helps
The solubility rules usually go on to say that group IIA sulfides are soluble, but actually group IIA sulfides react with water to make H2S and the group IIA metal hydroxide.
Answer:
The correct answer is 399.8 ppm
Explanation:
A concentration in parts per million (ppm) is equal to:

Solute: Cd; Mass = 180 mg x (1 g/1000 mg) = 0.18 g
Solvent: Water ; Mass= 450.0 g x (1 kg/1000 g) = 0.45 kg
We have the following total mass of solution:
Mass of solution = Mass of solute + Mass of solvent = 0.18 g + 450 g = 450.18 g = 0.45018 kg
Finally, we divide the <u>mass of solute (in mg)</u> into the <u>mass of solution (in kg)</u> to obtain the ppm (in mg/Kg):
ppm = 180 mg/0.45018 kg = 399.8 mg/Kg = 399.8 ppm