Answer:
10: Number of protons always equal number of electron, but that's the case with a neutral atom. ... This implies that it has same number of protons and electrons in it. It means it has same amount of positive and negative charge, which cancel each other, and the atom as a whole becomes electrically neutral.
19: The three stable isotopes of Argon, Argon-36, Argon-38, and Argon-40, would all have 18 protons and 18 electrons if they are all neutral. The three isotopes will have different numbers of neutrons compared to each other (18, 20, and 22 neutrons respectively).
20: This isotope of fluorine has 9 protons, 9 electrons and 10 neutrons.
Explanation: Hope those are the only answers you needed. I just saw the stars next to them and figure those were the only ones you needed.
