i believe the answer would be D. When ordered by atomics mass every eighth element has similar properties.
Formaldehyde is an organic compound.
Well, you could use a reverse osmosis process to remove all of the fluoride that the United Staes government has put in the water! Every year the Us Gov receives a lot of fluoride from china. Fluoride is a waste and a poison, and instead of the Us Government paying a Buch of money to burn this waste, they just put it in the water! what you need t do, is get your water from the earth. Which is actually the best place to get your water, because its WATER filtered by the earth. Just google wells or springs around your location, some private business/companies offer their water collecting serves, something you should really take advantage of! As for me, I get my water at a place called "Carlsbad alkaline water." good stuff, only 50 cents for 4 gallons. rawr XD Jesus loves you, and he offers the everything freely, which means you don't need to follow a religion to earn anything. Lets face it, your not perfect, and we need help from God!
Oxygen has 8 protons and 10 electrons due to the addition of 2 electrons, determined from the ion charge. Likewise an ion of potassium has 19 protons and 18 electrons. Charge on fluorine would be -1 and charge on calcium would be +2. Atomic number is the same as the number of protons, so it would be 6, the mass number is the sum of protons and neutrons which would be 13, and the charge is 0, as it is an atom and not an ion.