LecturePLUS Timberlake1 The Atom Atomic Number and Mass Number Isotopes (Take out your Periodic...
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Transcript of LecturePLUS Timberlake1 The Atom Atomic Number and Mass Number Isotopes (Take out your Periodic...
LecturePLUS Timberlake 1
The AtomAtomic Number and Mass Number
Isotopes
(Take out your Periodic Tables)
EQ’s1. What is the Atomic Theory?
2. What is an atom and how are its components arranged?
3. What is an isotope and how are neutrons related to isotopes?
4. How are isotopes and an element’s average atomic mass related?
LecturePLUS Timberlake 2
LecturePLUS Timberlake 3
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 4
Subatomic Particles
Particle Symbol Charge RelativeMass
Electron e- 1- 0
Proton p+ 1+ 1
Neutron n 0 1
LecturePLUS Timberlake 5
Location of Subatomic Particles
10-13 cm
electrons
protons
neutrons
10-8 cm
nucleus
LecturePLUS Timberlake 6
Atomic Number
Represents the number
of
protons
in an atom
LecturePLUS Timberlake 7
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 8
Periodic Table
1 2 3 4 5 6 7 8
11 Na
LecturePLUS Timberlake 9
Atomic Number on the Periodic Table
11
Na
Atomic Number
Symbol
LecturePLUS Timberlake 10
All atoms of an element have the same number of protons
11
Na
11 protons
Sodium
LecturePLUS Timberlake 11
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 12
Number of Electrons
An atom is neutral The net charge is zeroNumber of protons = Number of electronsAtomic number = Number of electrons
LecturePLUS Timberlake 13
Mass Number
Represents the number
of
protons and neutrons
in an atom
LecturePLUS Timberlake 14
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 37Cl17 17
chlorine - 35 chlorine - 37
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
LecturePLUS Timberlake 16
Atomic Symbols
Show the mass number and atomic number
Give the symbol of the element
mass number
23 Na sodium-23
atomic number 11
READING ISOTOPIC NOTATIONREADING ISOTOPIC NOTATION 46
21 Sc
46 = mass number (the total number of protons (2121) + neutrons (2525))
21 = atomic number (the total number of protons (2121))
Sc = element symbolIn a neutral atom, the number of electrons
(21) is equal to the number of protons.
LecturePLUS Timberlake 19
More Atomic Symbols
16 31 65
O P Zn
8 15 30
8 p+ 15 p+ 30 p+
8 n 16 n 35 n8 e- 15 e- 30 e-
LecturePLUS Timberlake 20
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 21
Solution AT 2
12C 13C 14C 6 6 6
#P __6___ _ 6___ ___6___
#N __6___ _ _7___ ___8___
#E __6___ _ 6___ ___6___
LecturePLUS Timberlake 22
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 23
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 O8
37 Cl17107 Ag47
LecturePLUS Timberlake 24
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 is1) 14 2) 16 3) 34
C. The element is1) Si 2) Ca 3) Se
D. Another isotope of this element is
1) 34X 2) 34X 3) 36X 16 14 14
LecturePLUS Timberlake 25
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 26
Atomic Mass
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
Na22.99
LecturePLUS Timberlake 27
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 28
Calculating Atomic Mass
Percent abundance of isotopes
Mass of each isotope of that element
Weighted average =
mass isotope1(%) + mass isotope2(%) + …
100 100
LecturePLUS Timberlake 29
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
Mg24.3
LecturePLUS Timberlake 30
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 31
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 32
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 33
Assign X and Y values:X = % 10B Y = % 11B
Determine Y in terms of XX + Y = 100Y = 100 - X
Solve for X:X (10.0) + (100 - X )(11.0) = 10.8
100 100
Multiply through by 10010.0 X + 1100 - 11.0X = 1080
LecturePLUS Timberlake 34
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 35
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 36
Solution AT8
2) 70%
Solution
62.9X + 6490 = 64.9X = 6350
-2.0 X = -140
X = 70%