Bellwork 9.12.2011
1.Draw a picture of an atom. Label the nucleus, protons, neutrons, and electrons.
2.Give the charges of each of the 3 subatomic particles.
3.Using the periodic table (or your knowledge), list 2 elements and describe their use to us!

Subatomic Particles
Particle Symbol Charge Relative
Mass
Electron e 10
Proton p + + 1
Neutron n 0 1

Atomic Number

Atomic Number on the
Periodic Table
Atomic Number
Symbol
11
Na

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

Learning Check
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

Mass Number
Counts the number of protons AND neutrons in an atom
We can find this, and the atomic number, in something called. . .

Atomic Symbol
Shows the mass number and atomic number
Na

• The difference between the mass
number and the atomic number . mass number – atomic number = # of Neutrons

How to find the # of Electrons
 An atom is neutral
 So the net charge is zero
 Number of protons = Number of electrons
 Atomic number = Number of electrons!

Subatomic Particles in Some
Atoms ep+ n
16
O
8
31
P
15
65
30
Zn

Isotopes
 Atoms with the same number of protons, but different numbers of neutrons.
 In other words. . . atoms of the same element
(same atomic number) with different mass numbers

Isotopes of Helium
Isotopes of Carbon

Learning Check
Naturally occurring carbon consists of three isotopes , 12 C, 13 C, and 14 C.
12 C
6
13 C 14
6 6
C
#p _______ _______ _______
#n _______ _______ _______
#e _______ _______ _______

Learning Check
An atom of zinc (Zn) 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

Learning Check
Write the atomic symbols for atoms with the following:
A. 8 p + , 8 n, 8 e ___________
B. 17p + , 20n, 17e ___________

Atomic Mass on the Periodic
Table
Atomic Number
Symbol
Atomic Mass
11
Na
22.99

Atomic Mass
Atomic mass is the weighted average mass of all the isotopes of that atom.
11
Na
22.99

Example of an Average Atomic
Mass
Cl-35 is about 75.5 % and Cl-37 about
24.5% of natural chlorine.

Bell Work 9/13/2011
1. What is the atomic number?
2. What is the mass number?
3. Complete the following and give there element names:
14 C 44 Ca
6
80
20 34
Se
#p _______ _______ _______
#n _______ _______ _______
#e _______ _______ _______

• An arrangement of elements in which the elements are separated into groups based on properties.

• The elements are listed by increasing atomic number

• Each horizontal row , there are seven

• Each vertical column
• Elements that share the same group have similar chemical and physical properties .

If you didn’t finish these during class do the following for homework:
• p. 111 #15 and 16
• p. 112 #17 and 18
• p. 113 #19 and 20
• p. 116 #21 and 22
• p. 117 #23 and 24