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The Atom Atomic Number and

LecturePLUS Timberlake 1 Atomic Theory

 Atoms are building blocks of elements  Similar atoms in each element  Different from atoms of other elements  Two or more different atoms bond in simple ratios to form compounds

LecturePLUS Timberlake 2 Subatomic Particles

Particle Symbol Charge Relative Mass

Electron e- 1- 0

Proton p+ + 1

Neutron n 0 1

LecturePLUS Timberlake 3 Location of Subatomic Particles

10-13 cm electrons

nucleus neutrons

-8 10 cm LecturePLUS Timberlake 4 Atomic Number

Counts the number of protons in an atom

LecturePLUS Timberlake 5 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 6 Periodic Table

1 2 3 4 5 6 7 8

11 Na

LecturePLUS Timberlake 7 Atomic Number on the Periodic Table

Atomic Number 11 Symbol Na

LecturePLUS Timberlake 8 All atoms of an element have the same number of protons

11 protons 11 Na

LecturePLUS Timberlake 9 Learning Check AT 1

State the number of protons for atoms of each of the following: A. 1) 5 protons 2) 7 protons 3) 14 protons B. 1) 32 protons 2) 16 protons 3) 6 protons C. 1) 137 protons 2) 81 protons 3) 56 protons LecturePLUS Timberlake 10

Solution AT 1

State the number of protons for atoms of each of the following: A. Nitrogen 2) 7 protons B. Sulfur 2) 16 protons C. Barium 3) 56 protons LecturePLUS Timberlake 11 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 12 Mass Number

Counts the number of protons and neutrons in an atom

LecturePLUS Timberlake 13 Atomic Symbols

 Show the mass number and atomic number  Give the symbol of the element

mass number 23 Na sodium-23 atomic number 11

LecturePLUS Timberlake 14 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- 15 e- 30 e- LecturePLUS Timberlake 15 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 35Cl 37Cl 17 17

chlorine - 35 LecturePLUS chlorine Timberlake - 37 16

Learning Check AT 2

Naturally occurring 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 ______17

Solution AT 2

12C 13C 14C 6 6 6 #P __6___ _ 6______6___

#N __6___ _ _7______8___

#E __6___ _ 6______6___

LecturePLUS Timberlake 18

Learning Check AT 3

An atom of 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 with 37 neutrons? 1) 37 2) 65 3) 67 LecturePLUS Timberlake 19

Solution AT 3

An atom of zinc has a mass number of 65. A. Number of protons in the zinc atom 1) 30 B. Number of neutrons in the zinc atom 2) 35

C. What is the mass number of a zinc isotope with 37 neutrons? 3) 67 LecturePLUS Timberlake 20 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- ______

LecturePLUS Timberlake 21

Solution AT 4

16O + - 8 A. 8 p , 8 n, 8 e B. 17p+, 20n, 17e- 37Cl 17

C. 47p+, 60 n, 47 e- 107Ag 47 LecturePLUS Timberlake 22 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 23

Solution AT 5

An atom has 14 protons and 20 neutrons. A. It has atomic number 1) 14

B. It has a mass number of 3) 34

C. The element is 1) Si D. Another isotope of this element would be 3) 36X LecturePLUS Timberlake 24 14

Masses of Atoms

 A scale designed for atoms gives their small atomic masses in 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 25

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 abundance %  Atomic mass is not a whole number

LecturePLUS Timberlake 26

Learning Check AT6

Using the periodic table, specify the atomic mass of each element (round to the tenths place): A. ______B. aluminum ______C. ______D. barium ______E. ______LecturePLUS Timberlake 27

Solution AT6

Using the periodic table, specify the atomic mass of each element (round to the tenths place): A. calcium _40.1 amu _ B. aluminum _27.0 amu _ C. lead _207.2 amu_ D. barium _137.3 amu_ E. iron _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

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 30 Learning Check AT7

Gallium is a metallic element found in small lasers used in compact disc players. In a sample of , 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 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 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 % abundance of each boron isotope?

LecturePLUS Timberlake 33 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 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 % abundance of each isotope? (Hint: Check periodic table for atomic mass)

1) 30% 2) 70% 3) 100%

LecturePLUS Timberlake 36 Solution AT8

2) 70%

Solution

62.9X + 6490 = 64.9X = 6350 -2.0 X = -140 X = 70%

LecturePLUS Timberlake 37