The two are potassium and rubidium. Why? Na is an alkali metal. As you go down the metals become more reactive.
Calcium has 20 protons. Why? The atomic # is 20 (the one at the top).
It has 20 neutrons. Why? The atomic mass (the number on the bottom) is ~40, ignoring electron mass. 40- 20 protons = 20 neutrons.
It has 20 electrons.
Why? The # of protons and electrons is the same. Ions aren't on the periodic table.
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Explanation:
Though cases of a dog being affected by poison ivy are rare, if you have a canine companion with sensitive skin, you should keep him away from the plant, just in case. “After being in an area with poison ivy or oak, you should wash your dog,” Nold suggests.
