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How many electrons are present in a chromium-52 atom? 24 electrons How many protons are present in a chromium-52 atom? 24 protons How many neutrons are present in a chromium-52 atom? 28 neutrons Give the number of protons, neutrons, and electrons in the 106Pd2+ ion. 46 protons 60 neutrons 44 electrons +2 ion indicates 2 more positives than negatives meaning that two electrons have been lost You have a neutral atom that has atomic number 77 and a mass number of 192. How many protons, neutrons, and electrons does it have? 77 protons 115 neutrons 77 electrons since neutral, #protons = #electrons How many paired electrons are in a germanium atom? How many unpaired electrons are in this atom? 30 paired, 2 unpaired [Ar] 4s2 3d10 4p2 Hund’s Rule says that in 4p, the electrons will enter each orbital one at a time until each orbital has at least one electron Give the orbital filling diagram for germanium (shorthand okay). [Ar] 4s 3d 4p Electrons will go to the place of ________ energy first. This is attributed to the _______ _________. Lowest; Aufbau principle No two electrons in an atom can have the same set of 4 quantum numbers. This statement is an illustration of ?? The Pauli exclusion principle Give the number of protons, neutrons, and electrons in the 127I-1 ion. 53 protons 74 neutrons 54 electrons -1 indicates that this atom has gained 1 electron since there is a negative charge indicating one more electron than proton In order for an electron to move away from the nucleus to an outer energy level, it must _____ energy. Gain; in lab, we provided energy with the Bunsen burner flame permitting electrons to escape ground state and move to excited state If an electron falls back toward the nucleus, we observe a change in energy that corresponds to colors of different wavelength. What happens to the energy of the electron? As the electron moves back toward the nucleus, it gives off energy falling back to the original energy level. The visible spectrum ranges in color from red to violet and in wavelength from ?? Red 700 nm – highest wavelength Violet 400 nm – lowest wavelength A photon of light has a frequency of 6.3 x 1015 Hz. What is its wavelength, in cm? The speed of light = 3 x 108 m/sec. = c/ = 3 x 108 m/sec = 4.76 x 10-8 m 6.3 x 1015 /sec 4.76 x 10-8 m ( 100 cm ) = 4.76 x 10-6 cm A particle is found to have a wavelength of 450 nm. What is its frequency? The speed of light = 3 x 108 m/sec. = c/ = 1014 Hz 3 x 108 m/sec = 6.7 x 4.5 x 10-7 m Determine the energy that a particle with frequency of 9.6 x 1014/sec has. Planck’s constant is 6.63 x 10-34J-sec. E = h = 6.63 x 10-34J-sec(9.6 x 1014/sec) E = 6.37 x 10-19J What is the energy of a particle that has a wavelength of 0.000075 cm? Planck’s constant is 6.63 x 10-34 J-sec. E = h However, we don’t have and cm:m issue = c/ = 3 x 108 m/sec = 4 x 1014/sec 7.5 x 10-7 m Then E = h 6.63 x 10-34 J-sec(4 x 1014/sec) 2.65 x 10-19J The energy of a particle is found to be 6.2 x 10-19 J. What frequency is associated with this particle? Planck’s constant is 6.63 x 10-34 J-sec. E = h You have energy and Planck’s constant so rearrange to solve for . E/h = 6.2 x 10-19 J = 9.35 x 1014/sec 6.63 x 10-34 J-sec It was determined that the energy of a photon is 7.3 x 10-19 J. What is the wavelength of the photon? Planck’s constant is 6.63 x 10-34 J-sec and the speed of light = 3 x 108 m/sec. E = h rearranging, we have E/h = 7.3 x 10-19 J = 1.1 x 1015/sec 6.63 x 10-34 J-sec then = c/ = 3 x 108 m/sec = 2.73 x 10-7m 1.1 x 1015/sec Lithium in nature occurs as a mixture of 6Li atoms with a mass of 6.015 amu and 7Li with a mass of 7.016 amu. The atomic mass of lithium is 6.941. What is the percent abundance of each of the two isotopes? x + y = 1 x = 1 – y 6.941 6.941 6.941 6.941 0.926 0.925 = = = – = = 6.015 (x) + 7.016 (y) 6.015 (1 – y) + 7.016y 6.015 – 6.015y + 7.016y 6.015 = 7.016y – 6.015y 1.001y y therefore, 6Li occurs 7.5% of the time and 7Li occurs 92.5% of the time. This answer makes sense as the atomic mass is much closer to the mass of the heavier isotope indicating that it should have a much greater abundance than 6Li. Atoms of the same element that vary in number of neutrons and therefore also in mass are called ?? Isotopes Atoms of an element that carry a charge due to either a gain or loss of electrons are known as ?? Ions When an atom gains electrons, it will have a ___ charge. Negative because it has more electrons (-) than protons (+) Which particle always remains the same for the same element? Protons remain the same because protons define the element. The number of protons is given by the ?? atomic number The sum of the number of protons plus the number of neutrons is called the ?? Mass number If an element consists of 60.1% of atoms with a mass of 68.926 amu and the remainder of the atoms have a mass of 70.925 amu, what is the atomic mass of the element? Based on this mass, what do you think the identity of the element is? 100% - 60.1% = 39.9% of isotope 2 AM = 68.926 (0.601) + 70.925 (0.399) AM = 69.723 amu Looking at the periodic table, this element may be gallium as it seems to be closest. Give the quantum numbers for the valence electrons in Mg. Magnesium has the configuration 1s2 2s2 2p6 3s2. The valence electrons are the two in the 3s sublevel. 3s1 3s2 n = 3, l = 0, ml = 0, ms = ½ n = 3, l = 0, ml = 0, ms = -½ Give the orbital filling diagram and the full electron configuration for molybdenum. Tungsten (W) consists of two isotopes. 183W has a mass of 183.26 amu and 184W has a mass of 184.72 amu. Determine the abundance of each isotope of tungsten. First, go to the periodic table to obtain the atomic mass of tungsten (183.84 amu). Then, set up your equation. 183.84 = (183.26)(x) + 184.72(y) We know that x + y = 1; thus, y = 1-x Substitute for y in the equation. 183.84 = 183.26x + 184.72(1-x) 183.84 = 183.26x + 184.72 – 184.72x 183.84 – 184.72 = 183.26x – 184.72x -0.88 = -1.46x 0.603 = x 0.391 = y Thus, 183W occurs 60.3% of the time and 184W occurs 39.1% of the time.