This document discusses the structure of atoms including subatomic particles like protons, neutrons, and electrons. It explains key atomic concepts such as atomic number, mass number, isotopes, and the periodic table. The periodic table arranges elements by atomic number and can be used to find protons, electrons, atomic symbols, and average atomic masses. Atoms of the same element have the same number of protons.

1. The Atom
Atomic Number and Mass
Number
Isotopes
LecturePLUS Timberlake
1

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
LecturePLUS Timberlake
2

3. Subatomic Particles
Particle
Symbol
Charge
Relative
Mass
Electron
e-
1-
0
Proton
p+
+
1
Neutron
n
0
1
LecturePLUS Timberlake
3

4. Location of Subatomic Particles
10-13 cm
electrons
protons
nucleus
10-8 cm
LecturePLUS Timberlake
neutrons
4

5. Atomic Number
Counts the number
of
protons
in an atom
LecturePLUS Timberlake
5

6. 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

7. Periodic Table
1
2
3
4
5
6
7
8
11
Na
LecturePLUS Timberlake
7

8. Atomic Number on the Periodic
Table
Atomic Number
Symbol
11
Na
LecturePLUS Timberlake
8

9. All atoms of an element have
the same number of protons
11 protons
Sodium
11
Na
LecturePLUS Timberlake
9

10. Learning Check AT 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
C. Barium
1) 137 protons 2) 81 protons
LecturePLUS Timberlake
3) 6 protons
3) 56 protons
10

11. 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

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. Mass Number
Counts the number
of
protons and neutrons
in an atom
LecturePLUS Timberlake
13

14. 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
14

15. More Atomic Symbols
16
31
O
8
8 p+
8n
8 e-
65
P
15
Zn
30
15 p+
30 p+
16 n
35 n
LecturePLUS
15 e- Timberlake
30 e-
15

16. 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
12
C
An atom twice as heavy has a mass of 24.00
amu. An atom half as heavy is 6.00 amu. 16
LecturePLUS Timberlake

17. 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
17

18. 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
__________
LecturePLUS Timberlake
18

19. 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
19