Chapter 12 The Atom & Periodic Table- part 2 Electrons found outside the nucleus; negatively charged Protons found in the nucleus; positive charge equal in magnitude to the electron s negative charge Neutrons found in the nucleus; no charge; virtually same mass as a proton Summary from last time Greek Atomos ~400BC Dalton 1800AC Thomson + Millikan (Plum model) Rutherford Orbits Bohr model Orbitals Quantum 1
Atomic Notation Each element has a characteristic number of protons in the nucleus. This is the atomic number, Z. The total number of protons and neutrons in the nucleus of an atom is the mass number, A. We use atomic notation to display the number of protons and neutrons in the nucleus of an atom: X Isotopes All atoms of the same element have the same number of protons. Most elements occur naturally with varying numbers of neutrons. Atoms of the same element that have a different number of neutrons in the nucleus are called isotopes. Isotopes have the same atomic number, but different mass numbers. 2
Learning Check There are three naturally occurring isotopes of carbon: 12 C, 13 C, and 14 C. State the number of protons, neutrons, and electrons in each of these isotopes. #p #n #e Using Atomic Notation If a neutral element has the following chemical symbol, how many electrons does it have? U A) 92 B) 82 C) 235 D) 143 E) none of the above 3
Atomic Notation Periodic Table Notation Average mass The average mass is calculated by multiplying the mass for each isotope by the fraction of the isotope (%/100) and adding the numbers together. Average mass= (mass of isotope 1)(fraction abundance of isotope 1) + (mass of isotope 2)(fraction abundance of isotope 2) + 4
All Isotopes are NOT Created Equal isotope mass 1abundance 1 isotope mass 2abundance 2 average atomic mass 35 Cl = 34.9689 amu % Abundance = 75.77% 37 Cl = 36.9659 amu % Abundance = 24.23% => 0.7577 => 0.2423 + 34.9689 x 0.7577 + 36.9659 x 0.2423 = 35.45amu isotope mass 1 abundance 1 isotope mass 2 abundance 2 average atomic mass Where have I seen this before? Periodic Table gives AVERAGE ATOMIC MASS in amu!! Average Atomic Mass Ex: Gallium has two isotopes: 1. 69 Ga, with a mass of 68.926 u and 60.11% abundance. 2. 71 Ga, with a mass of 70.925 u and 39.89% abundance. Average mass= (mass of isotope 1)(fraction abundance of isotope 1) + (mass of isotope 2)(fraction abundance of isotope 2) + The average atomic mass of copper is: (68.926 u)(0.6011) + (70.925 u)(0.3989) = 69.72 u 5
Isotopes and Atomic Mass The element bromine, Br (atomic number 35), has two major isotopes of similar abundance, both around 50 percent. The atomic mass of bromine is reported in the periodic table as 79.904 atomic mass units. Choose the most likely set of mass numbers for these two bromine isotopes. A) Br-80, Br-81 B) Br-79, Br-80 C) Br-79, Br-81 D) Br-78, Br-80 Summary from last time Greek Atomos ~400BC Dalton 1800AC Thomson + Millikan (Plum model) Rutherford Orbits Bohr model Orbitals Quantum 6
Bohr Model Protons found in the nucleus; positive charge equal in magnitude to the electron s negative charge Neutrons no charge; found in the nucleus; virtually same mass as a proton Electrons negatively charged; found outside the nucleus moving in circular orbits; they can jump between levels by absorbing or emitting photons of a particular wavelength Bohr Model of H Atoms 15 7
Quantum Mechanical Model of the Atom An orbital is the region of space where there is a high probability (90%) of finding an atom. In the quantum mechanical atom, orbitals are arranged according to their size and shape. The higher the energy of an orbital, the larger its size. All s orbitals have spherical shapes. Shapes of the s, p, d and f Orbitals Sublevels 8
Element Symbols Each element has its own unique symbol. One or two letter symbols are used to represent elements. Most of the time, the symbol is derived from the name of the element. The first letter is always capitalized and the second letter is always a lower case. Examples: C is the symbol for carbon Cr is the symbol for chromium Copper: The origin of the name comes from the Latin word cuprum meaning the island of Cyprus famed for its copper mines Iron: The origin of the name comes from the Latin word ferrum meaning iron. The Periodic Table and the Elements What is the periodic table? What information is obtained from the table? How can elemental properties be predicted base on the PT? Different periodic tables can include various bits of information, but usually: atomic number symbol atomic mass number of valence electrons state of matter at room temperature. 9
Dmitri Mendeleev (1869) Mendeleev proposed that the properties of the chemical elements repeat at regular intervals when arranged in order of increasing atomic mass. Mendeleev is the architect of the modern periodic table. He arranged his periodic table in columns by the formula of the element s oxide. Chemistry Connection: Dmitri Mendeleev Dmitri Mendeleev was born in Siberia in 1834 as the youngest of 14 to 17 children. He was a student and professor at the University of St. Petersburg. Based on periodic trends, Mendeleev predicted the existence of three elements (gallium, scandium, and germanium) before they were discovered. He narrowly missed being awarded the Nobel Prize in 1906. 10
The Periodic Table Most elements are metals and occur on the left side. The nonmetals appear on the right side. Metalloids (semimetals) are elements that have some metallic and some nonmetallic properties. Groups and Periods of Elements A vertical column on the periodic table is a group or family of elements. A horizontal row on the periodic table is a period or series of elements. There are 18 groups and seven periods on the periodic table. IA 1 1 H 1.01 3 Li 6.94 11 Na 22.99 19 K 39.10 37 Rb 85.47 55 Cs 132.91 87 Fr (223) IIA 2 4 Be 9.01 12 Mg 24.31 20 Ca 40.08 38 Sr 87.62 56 Ba 137.33 88 Ra (226) IIIB 3 21 Sc 44.96 39 Y 88.91 57 La 138.91 89 Ac (227) IVB 4 22 Ti 47.88 40 Zr 91.22 72 Hf 178.49 104 Rf (261) VB 5 23 V 50.94 41 Nb 92.91 73 Ta 180.95 105 Db (262) 58 Ce 140.12 90 Th (232) VIB 6 24 Cr 52.00 42 Mo 95.94 74 W 183.85 106 Sg (263) 59 Pr 140.91 91 Pa (231) VIIB 7 25 Mn 54.94 43 Tc (99) 75 Re 186.21 107 Bh (262) 60 Nd 144.24 92 U (238) VIII 8 26 Fe 55.85 44 Ru 101.07 76 Os 190.2 108 Hs (265) 61 Pm (147) 93 Np (237) VIII 9 27 Co 58.93 45 Rh 102.91 77 Ir 192.22 109 Mt (266) 62 Sm 150.36 94 Pu (244) VIII 10 28 Ni 58.69 46 Pd 106.42 78 Pt 195.08 110 Ds (271) 63 Eu 151.97 95 Am (243) IB 11 29 Cu 63.55 47 Ag 107.87 79 Au 196.97 111 Rg (272) 64 Gd 157.25 96 Cm (247) IIB 12 30 Zn 65.39 48 Cd 112.41 80 Hg 200.59 112 -- (277) 65 Tb 158.93 97 Bk (247) IIIA 13 5 B 10.81 13 Al 26.98 31 Ga 69.72 49 In 114.82 81 Tl 204.38 66 Dy 162.50 98 Cf (251) IVA 14 6 C 12.01 14 Si 28.09 32 Ge 72.61 50 Sn 118.71 82 Pb 207.2 114 -- (285) 67 Ho 164.93 99 Es (252) VA 15 7 N 14.01 15 P 30.97 33 As 74.92 51 Sb 121.75 83 Bi 208.98 68 Er 167.26 100 Fm (257) VIA 16 8 O 16.00 16 S 32.07 34 Se 78.96 52 Te 127.60 84 Po (209) 116 -- (289) 69 Tm 168.93 101 Md (258) VIIA 17 9 F 19.00 17 Cl 35.45 35 Br 79.90 53 I 126.90 85 At (210) 70 Yb 173.04 102 No (259) VIIIA 18 2 He 4.00 10 Ne 20.18 18 Ar 39.95 36 Kr 83.80 54 Xe 131.29 86 Rn (222) 71 Lu 174.97 103 Lr (260) 11
Common Names of Groups (Families) Several families have common trivial names. Group I are the alkali metals. Group II are the alkaline earth metals. Group VII (17) are the halogens. Group VIII (18) are the noble gases. The Periodic Table 12
Atomic radius examples Which of the following elements has the smallest atomic radius? F Cl Br O S Common Names of Groups (Families) 13