Transcript
Page 1: LecturePLUS Timberlake 1 The Atom Atomic Number and Mass Number Isotopes

LecturePLUS Timberlake1

The Atom

Atomic Number and Mass Number

Isotopes

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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

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Subatomic Particles

Particle Symbol Charge RelativeMass

Electron e- - 0

Proton p+ + 1

Neutron n 0 1

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Location of Subatomic Particles

10-13 cm

electrons

protons

neutrons

10-8 cm

nucleus

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Atomic Number

Counts the number

of

protons

in an atom

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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

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Periodic Table

1 2 3 4 5 6 7 8

11 Na

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Atomic Number on the Periodic Table

11

Na

Atomic Number

Symbol

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All atoms of an element have the same number of protons

11

Na

11 protons

Sodium

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Learning Check #1

State the number of protons for atoms of each of the following:

A. Nitrogen

1) 5 protons 2) 7 protons 3) 14 protons

B. Sulfur

1) 32 protons 2) 16 protons 3) 6 protons

C. Barium

1) 137 protons 2) 81 protons 3) 56 protons

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Number of Electrons

An atom is neutral The net charge is zeroNumber of protons = Number of electronsAtomic number = Number of electrons

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Mass Number

Counts the number

of

protons and neutrons

in an atom

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Atomic Symbols

Show the mass number and atomic number

Give the symbol of the element

mass number

23 sodium-23

atomic number 11Na

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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-

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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

35 37

17 17

chlorine - 35 chlorine - 37

Cl Cl

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Learning Check #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.

12 13 14

6 6 6

#P _______ _______ _______

#N _______ _______ _______

#E _______ _______ _______

C C C

6

6

6

6

7

6

6

8

6

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Solution #2

12C 13C 14C 6 6 6

#P __6___ _ 6___ ___6___

#N __6___ _ _7___ ___8___

#E __6___ _ 6___ ___6___

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Learning Check #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

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Learning Check #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- ___________

O16

8

Cl37

17

Ag107

47

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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) 34 2) 34 3) 36

16 14 1420

Learning Check #5

X X X

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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.

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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

abundance %

Atomic mass is not a whole number

Na22.99


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