Chapter 2
Atoms and Elements
The Atom
Atomic Number and Mass Number
Isotopes

1
Atomic Theory

Atoms are building blocks of elements
Similar atoms in each element
Different from atoms of other elemen...
Subatomic Particles
Particle

Symbol

Charge

Relative
Mass
0

Electron

e-

1-

Proton

p+

+

1

Neutron

n

0

1

3
Location of Subatomic Particles
10-13 cm
electrons
protons
nucleus

neutrons

10-8 cm
4
Atomic Number

Counts the number
of
protons
in an atom
LecturePLUS Timberlake

5
Atomic Number on the Periodic
Table
Atomic Number

Symbol

11

Na
6
All atoms of an element have the
same number of protons
11 protons
Sodium

11

Na
7
Learning Check
State the number of protons for atoms of each of
the following:
A. Nitrogen
1) 5 protons
2) 7 protons 3) 14...
Solution
State the number of protons for atoms of each of the
following:
A. Nitrogen
2) 7 protons
B. Sulfur
2) 16 protons
...
Mass Number

Counts the number
of
protons and neutrons
in an atom

10
Atomic Symbols
Show the mass number and atomic number
Give the symbol of the element
mass number
23

atomic number

Na

...
Number of Electrons
An atom is neutral
The net charge is zero
Number of protons = Number of electrons
Atomic number = ...
Subatomic Particles in Some
Atoms
16

O

8

8 p+
8n
8 e-

31

P

15

65

Zn

30

15 p+
16 n
15 eLecturePLUS Timberlake

30...
Isotopes
Atoms with the same number of protons, but
different numbers of neutrons.
Atoms of the same element (same atomi...
Learning Check
Naturally occurring carbon consists of three isotopes,
12
C, 13C, and 14C. State the number of protons, neu...
Solution
12

C

6

13
6

C

14
6

#p

6

6

6

#n

6

7

8

#e

6

6

C

6

LecturePLUS Timberlake

16
Learning Check
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 ...
Solution
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...
Learning Check
Write the atomic symbols for atoms with the
following:
A. 8 p+, 8 n, 8 e-

___________

B. 17p+, 20n, 17e-
...
Solution
16

O

A. 8 p+, 8 n, 8 e-

8

B. 17p+, 20n, 17e-

37
17

C. 47p+, 60 n, 47 e-

Cl

107

Ag

47
LecturePLUS Timber...
Atomic Mass on the Periodic
Table
Atomic Number
Symbol

Atomic Mass

11

Na
22.99
21
Atomic Mass
Atomic mass is the weighted average mass
of all the atomic masses of the isotopes of
that atom.

22
Example of an Average Atomic
Mass
Cl-35 is about 75.5 % and Cl-37 about
24.5% of natural chlorine.
35 x 75.5 = 26.4
100
35...
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Atoms

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Atoms

  1. 1. Chapter 2 Atoms and Elements The Atom Atomic Number and Mass Number Isotopes 1
  2. 2. 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 2
  3. 3. Subatomic Particles Particle Symbol Charge Relative Mass 0 Electron e- 1- Proton p+ + 1 Neutron n 0 1 3
  4. 4. Location of Subatomic Particles 10-13 cm electrons protons nucleus neutrons 10-8 cm 4
  5. 5. Atomic Number Counts the number of protons in an atom LecturePLUS Timberlake 5
  6. 6. Atomic Number on the Periodic Table Atomic Number Symbol 11 Na 6
  7. 7. All atoms of an element have the same number of protons 11 protons Sodium 11 Na 7
  8. 8. Learning Check 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 LecturePLUS Timberlake 8
  9. 9. Solution 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 9
  10. 10. Mass Number Counts the number of protons and neutrons in an atom 10
  11. 11. Atomic Symbols Show the mass number and atomic number Give the symbol of the element mass number 23 atomic number Na sodium-23 11 LecturePLUS Timberlake 11
  12. 12. 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
  13. 13. Subatomic Particles in Some Atoms 16 O 8 8 p+ 8n 8 e- 31 P 15 65 Zn 30 15 p+ 16 n 15 eLecturePLUS Timberlake 30 p+ 35 n 30 e13
  14. 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 35 17 Cl chlorine - 35 37 17 Cl chlorine - 37 LecturePLUS Timberlake 14
  15. 15. Learning Check Naturally occurring carbon consists of three isotopes, 12 C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12 C 6 13 C 6 14 C 6 #p _______ _______ _______ #n _______ _______ _______ #e _______ _______ _______ LecturePLUS Timberlake 15
  16. 16. Solution 12 C 6 13 6 C 14 6 #p 6 6 6 #n 6 7 8 #e 6 6 C 6 LecturePLUS Timberlake 16
  17. 17. Learning Check 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 17
  18. 18. Solution 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 18
  19. 19. Learning Check 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 19
  20. 20. Solution 16 O A. 8 p+, 8 n, 8 e- 8 B. 17p+, 20n, 17e- 37 17 C. 47p+, 60 n, 47 e- Cl 107 Ag 47 LecturePLUS Timberlake 20
  21. 21. Atomic Mass on the Periodic Table Atomic Number Symbol Atomic Mass 11 Na 22.99 21
  22. 22. Atomic Mass Atomic mass is the weighted average mass of all the atomic masses of the isotopes of that atom. 22
  23. 23. Example of an Average Atomic Mass Cl-35 is about 75.5 % and Cl-37 about 24.5% of natural chlorine. 35 x 75.5 = 26.4 100 35.5 37 x 24.5 = 9.07 100 23

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