I need help with the following multiple choice questions, your help is greatly appreciated.After 32 days, 5 milligrams of an 80-milligram sample of a radioactive isotope remains unchangedWhat is the half-life of this element?1) 8 days 2) 2 days 3) 16 days 4) 4 daysWhat is the total mass of 222Rn remaining in an original 160-milligram sample of 222Rn after 19.1 days? 1) 2.5 mg 2) 5.0 mg 3) 10mg 4) 20mgWhich element forms an ion that is larger than its atom?1) aluminum 2) chlorine 3) magnesium 4) sodiumWhich element is so active chemically that it occurs naturally only in compounds?1) potassium 2) silver 3) copper 4) sulfur
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First question: One half-life leaves 40 mg, two leaves 20 mg, three leaves 10 mg, and four leaves 5 mgSo the half-life is 32 divided by 4, which is 8So the answer is 8 days (1)Second question: The half-life of 222Rn is 3.825 days, so 19.1 is five times its half-lifeSo there will be 160/(2^5) mg left, so the answer is 5 mg (2)Third question: Aluminum, magnesisum, and sodium all form positive ions, which means that they lose electrons, so they get smallerChlorine forms a negative ion, so it gains an electron and hence gets biggerSo the answer is chlorine (2)Fourth question: Potassium, and all the elements in that column of the periodic table are highly reactiveSilver and copper are both common metals that you might see in jewlrey and coins, and are mined from certain rocks, where it is found naturally in small pocketsSulfur occurs naturally around volcanosSo the answer is potassium (1).
