Bromine has two naturally occurring isotopes; 79Br (mass of 78.918) and 81Br (mass of 80.916). If the atomic weight of bromine is 79.904, predict the mass spectrum of a sample of bromine atoms. (LO 2.17) (a)
(b)
(c)
(d)

Which sample has the greatest mass? (LO 2.16)(a) 5.5 mol of C (b) 2.1 mol of S (c) 4.2 mol of Be (d) 0.52 mol of Ag

How many protons, neutrons, and electrons are in 107Ag+? (LO 2.21)(a) protons = 47, neutrons = 60, electrons = 46 (b) protons = 47, neutrons = 107, electrons = 48 (c) protons = 60, neutrons = 47, electrons = 47 (d) protons = 47, neutrons = 107, electrons = 46

Which experiment and subsequent observation led to the discovery that atoms contain negatively charged particles, now known as electrons? (LO 2.10–2.12)(a) Oil is sprayed into a chamber and the speed at which the oil droplets fall is measured with and without an applied voltage. X rays in the chamber knock electrons out of air molecules. The electrons stick to the oil pro-ducing an overall negative charge on the drops. Adjusting the voltage changes the speed at which the negatively charged oil droplets fall. (b) When a high voltage is applied across metal electrodes at opposite ends of a sealed glass tube, a cathode ray is produced. The cathode ray is repelled by a negatively charged plate. (c) A radioactive substance emits alpha particles, which are directed at a thin gold foil. Most of the alpha par-ticles pass through the foil, but a few alpha particles are slightly deflected and some even bounce back toward the radioactive source. (d) The mass of different elements in a pure chemical com-pound are measured. Different samples of the compound always contains the same proportion of elements by mass.

How many atoms are present in 1.2 g of gold? (LO 2.16)(a) 2.5 * 1021 (b) 1.4 * 1026 (c) 7.2 * 1023 (d) 3.7 * 1021