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Atomic Weight

Atoms Lesson - Atomic Weight - Atom Mass Number - Science Lessons & Tests - My Schoolhouse - Online Learning
 

Atoms have charges.  There are two kinds of charges.  There are positive (+) charges and negative (-) charges.  Scientists have discovered that some parts of an atom have positive charges and other parts have negative charges.

PROTONS - have positive charges (+)

ELECTRONS - have negative charges (-)

NEUTRONS - have no charges.  They are neutral.

The number of protons in the nucleus of an atom determines an element's Atomic Number.  An atom has the same number of protons and electrons.  In the diagram below, there are 2 protons and 2 electrons.  The Atomic Number of the element below would be 2.

Atom Picture

The number of neutrons and protons of an atom is called the atom's Mass Number.

Each PROTON is given a mass of one.

Each NEUTRON is given a mass of one.

Here's an example:

Name of Element

Number of Protons

Number of Neutrons

Mass Number

cobalt

27

32

59

 

Practice finding the atom's Mass Number for each of the elements listed below.  Remember the atom's  Mass Number equals the sum of the protons and neutrons.

Name of Element

Number of Protons

Number of Neutrons

Mass Number

zinc 30 35
krypton 36 48
potassium 19 20
silver 47 61
lead 82 125
oxygen 8 8
hydrogen 1 0

calcium

20

20

 

Directions: Answer the questions about atoms.

1. A has a positive charge.

2. An  has a negative charge.

3. A has no charge.

4. The number of and protons of an atom is called the atom's Mass Number.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


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