A) because when gas is produced it changes chemical form whereas the chemical change is obvious.
Answer:
Avogadro's number is 6.022×1023 molecules. With Avogadro's number, scientists can discuss and compare very large numbers, which is useful because substances in everyday quantities contain very large numbers of atoms and molecules.
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Because the nuclear charge increases across a period and so it has a stronger pull on the outer electrons and will pull in the radius
