Why would seeing how a substance reacts with vinegar help you classify the substance as a mixture?

You are making a solution of calcium chloride dissolved in water. you add solid, stir, and it dissolves. you add just a spatula tip full, stir, and the solid does not dissolve. how could you describe the solutions before and after adding the spatula tip amount

If two identical atoms are bonded,what kind of molecule is formed

If an atom has 12 protons and 13 neutrons