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CHEMISTRY – 11TH GRADE
ATOMS
OBJECTIVES
Students will learn:
Composition of an atom
Charges of subatomic particles
Location of subatomic particles
How to determine the number of each subatomic particle in an atom using the periodic table
WHAT ARE ATOMS MADE OF?
Atoms are composed of 3 types of subatomic particles:
Positively charged PROTONS
Negatively charged ELECTRONS
Neutral NEUTRONS (no charge)
WHERE ARE THESE SUBATOMIC PARTICLES FOUND IN THE ATOM?
Protons and neutrons are located in the nucleus; they never go outside of the nucleus
Electrons are found outside of the nucleus in the electron cloud
COMMON MODEL OF AN ATOM
USING THE PERIODIC TABLE
C6
12.0107
Atomic Number
Atomic Symbol
Atomic Mass
DETERMINING THE NUMBER OF PROTONS
The number of protons = the atomic number
C6
12.0107
Carbon is atomic number 6
Carbon has 6 protons
DETERMINING THE NUMBER OF ELECTRONS
The number of electrons = the atomic number
C6
12.0107
Carbon is atomic number 6
Carbon has 6 electrons
IMPORTANT NOTE Only in a neutral atom are the number of
protons and the number of electrons equal.
This is because the negative charge of the electron will cancel out the positive charge of the proton. This is just like a math problem where 1 + (-1) = 0
DETERMINING THE NUMBER OF NEUTRONS
The number of neutrons = atomic mass – atomic
number
C6
12.0107
Carbon is atomic number 6
Carbon has an atomic mass of 12 amu
12 – 6 =
6 neutrons
NUMBER OF SUBATOMIC PARTICLES IN CARBON
6 protons
6 electrons
6 neutrons
Let’s Practice!
Imagine you are a scientist working in the field and an atom of an unknown element has been discovered. You later find that the atom has 78 protons. What is the element?
Gold
Silver
Platinum
Mercury
Correct!
Next Question
Incorrect
Try Again
If a neutral atom was found and it contained 24 electrons, how many neutrons would there be?
26
25
28
30
Next Question
Correct!
Try Again
Incorrect
What is the name of the element (containing 24 electrons and 28 neutrons) discovered in the previous question?
Chromium
Manganese
Cobalt
Iron
Correct!
Next Question
Try Again
Incorrect
True or False: The number of electrons in an atom is always equal to the number of protons.
True
False
Correct!
References
Incorrect
Try Again
REFERENCES
Books:
Smith, J. G. (2010). General, organic, and biological chemistry. (2nd ed.). New York, NY: McGraw-Hill.
Images:
Image: “Thinker”
http://office.microsoft.com/en-us/images/results.aspx?qu=thinker&ex=2&AxInstalled=copy&Download=MM900043731&ext=GIF&c=0#ai:MM900043731|
Found on: office.microsoft.com
Image: “Stylized Atom 2”
http://openclipart.org/detail/47179/stylized-atom-2-by-j_alves
Found on: openclipart.org
