370 likes | 390 Views
Learn about atomic theory, the structure of atoms, isotopes, and the relationship between isotopes and average atomic mass in this informative lecture by Timberlake.
E N D
The Atom Atomic Number and Mass Number Isotopes (Take out your Periodic Tables) LecturePLUS Timberlake
EQ’s • What is the Atomic Theory? • What is an atom and how are its components arranged? • What is an isotope and how are neutrons related to isotopes? • How are isotopes and an element’s average atomic mass related? LecturePLUS Timberlake
Atomic Theory • Atoms are building blocks of elements • Each element has similar atoms • Different from atoms of other elements • Two or more different atoms bond in simple ratios to form compounds LecturePLUS Timberlake
Subatomic Particles Particle Symbol Charge Relative Mass Electron e- 1- 0 Proton p+ 1+ 1 Neutron n 0 1 LecturePLUS Timberlake
Location of Subatomic Particles 10-13 cm electrons protons neutrons 10-8 cm nucleus LecturePLUS Timberlake
Atomic Number Represents the number of protons in an atom LecturePLUS Timberlake
Periodic Table • Represents physical and chemical behavior of elements • Arranges elements by increasing atomic number • Repeats similar properties in columns known as chemical families or groups LecturePLUS Timberlake
Periodic Table 1 2 3 4 5 6 7 8 11 Na LecturePLUS Timberlake
Atomic Number on the Periodic Table 11 Na Atomic Number Symbol LecturePLUS Timberlake
All atoms of an element have the same number of protons 11 Na 11 protons Sodium LecturePLUS Timberlake
Learning Check AT 1 State the number of protons for atoms of each of the following: A. Nitrogen (N) 1) 5 protons 2) 7 protons 3) 14 protons B. Sulfur (S) 1) 32 protons 2) 16 protons 3) 6 protons C. Barium (Ba) 1) 137 protons 2) 81 protons 3) 56 protons LecturePLUS Timberlake
Number of Electrons • An atom is neutral • The net charge is zero • Number of protons = Number of electrons • Atomic number = Number of electrons LecturePLUS Timberlake
Mass Number Represents the number of protons and neutrons in an atom LecturePLUS Timberlake
Isotopes • Atoms with the same number of protons, but different numbers of neutrons. • Atoms of the same element (same atomic number) with different mass numbers Isotopes of chlorine 35Cl 37Cl 1717 chlorine - 35 chlorine - 37 LecturePLUS Timberlake
ISOTOPIC NOTATION A Z X A= mass number (the total number of protons + neutrons) Z= atomic number (the total number of protons) X= element symbol
Atomic Symbols • Show the mass number and atomic number • Give the symbol of the element mass number 23 Nasodium-23 atomic number11 LecturePLUS Timberlake
READING ISOTOPIC NOTATION 46 21 Sc 46 = mass number (the total number of protons (21) + neutrons (25)) 21 = atomic number (the total number of protons (21)) Sc= element symbol In a neutral atom, the number of electrons (21) is equal to the number of protons.
More Atomic Symbols 16 31 65 O P Zn 8 15 30 8 p+ 15 p+ 30 p+ 8 n 16 n 35 n 8 e- 15e- 30 e- LecturePLUS Timberlake
Learning Check AT 2 Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12C 13C 14C 6 6 6 #P _______ _______ _______ #N _______ _______ _______ #E _______ _______ _______ LecturePLUS Timberlake
Solution AT 2 12C 13C 14C 6 6 6 #P __6____ 6___ ___6___ #N __6___ __7___ ___8___ #E __6____ 6___ ___6___ LecturePLUS Timberlake
Learning Check AT 3 An atom of zinc has a mass number of 65. A. Number of protons in the zinc atom 1) 30 2) 35 3) 65 B. Number of neutrons in the zinc atom 1) 30 2) 35 3) 65 C. What is the mass number of a zinc isotope with 37 neutrons? 1) 37 2) 65 3) 67 LecturePLUS Timberlake
Learning Check AT 4 Write the atomic symbols for atoms with the following: A. 8 p+, 8 n, 8 e- ___________ B. 17p+, 20n, 17e- ___________ C. 47p+, 60 n, 47 e- ___________ 16 O 8 37 Cl 17 107 Ag 47 LecturePLUS Timberlake
Learning Check AT 5 An atom has 14 protons and 20 neutrons. A. Its atomic number is 1) 14 2) 16 3) 34 B. Its mass number is 1) 14 2) 16 3) 34 C. The element is 1) Si 2) Ca 3) Se D. Another isotope of this element is 1)34X 2)34X 3)36X 16 14 14 LecturePLUS Timberlake
Masses of Atoms • A scale designed for atoms gives their small atomic masses in atomic mass units (amu) • An atom of 12C was assigned an exact mass of 12.00 amu • Relative masses of all other atoms was determined by comparing each to the mass of 12C • An atom twice as heavy has a mass of 24.00 amu. An atom half as heavy is 6.00 amu. LecturePLUS Timberlake
Atomic Mass Na 22.99 • Listed on the periodic table • Gives the mass of “average” atom of each element compared to 12C • Average atom based on all the isotopes and their percent abundance (% abundance) • Atomic mass is not a whole number LecturePLUS Timberlake
Learning Check AT6 Using the periodic table, specify the atomic mass of each element (round to the tenths place): A. calcium __________ B. aluminum __________ C. lead __________ D. barium __________ E. iron __________ 40.1 amu 27.0 amu 207.2 amu 137.3 amu 55.8 amu LecturePLUS Timberlake
Calculating Atomic Mass • Percent abundance of isotopes • Mass of each isotope of that element • Weighted average = mass isotope1(%) + mass isotope2(%) + … 100100 LecturePLUS Timberlake
Atomic Mass of Magnesium Isotopes Mass of Isotope Abundance 24Mg = 24.0 amu 78.70% 25Mg = 25.0 amu 10.13% 26Mg = 26.0 amu 11.17% Atomic mass (average mass) Mg = 24.3 amu Mg 24.3 LecturePLUS Timberlake
Learning Check AT7 Gallium is a metallic element found in small lasers used in compact disc players. In a sample of gallium, there is 60.2% of gallium-69 (68.9 amu) atoms and 39.8% of gallium-71 (70.9 amu) atoms. What is the atomic mass of gallium? LecturePLUS Timberlake
Solution AT7 Ga-69 (%/100) 68.9 amu x 60.2 = 41.5 amu for 69Ga 100 Ga-71 (%/100) 70.9 amu x 39.8 = 28.2 amu for 71Ga 100 Atomic mass Ga = 69.7 amu LecturePLUS Timberlake
Finding An Isotopic Mass A sample of boron consists of 10B (mass 10.0 amu) and 11B (mass 11.0 amu). If the average atomic mass of B is 10.8 amu, what is the percent abundance of each boron isotope? LecturePLUS Timberlake
Assign X and Y values: X = % 10B Y = % 11B Determine Y in terms of X X + Y = 100 Y = 100 - X Solve for X: X (10.0) + (100 - X )(11.0) = 10.8 100 100 Multiply through by 100 10.0 X + 1100 - 11.0X = 1080 LecturePLUS Timberlake
Collect X terms 10.0 X - 11.0 X = 1080 - 1100 - 1.0 X = -20 X = -20 = 20 % 10B - 1.0 Y = 100 - X % 11B = 100 - 20% = 80% 11B LecturePLUS Timberlake
Learning Check AT8 Copper has two isotopes 63Cu (62.9 amu) and 65Cu (64.9 amu). What is the percent abundance of each isotope? (Hint: Check periodic table for atomic mass) LecturePLUS Timberlake
Solution AT8 2) 70% Solution 62.9X + 6490 = 64.9X = 6350 -2.0 X = -140 X = 70% LecturePLUS Timberlake