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

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Atomic Number

Atomic Symbol

Atomic Mass

DETERMINING THE NUMBER OF PROTONS

The number of protons = the atomic number

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Carbon is atomic number 6

Carbon has 6 protons

DETERMINING THE NUMBER OF ELECTRONS

The number of electrons = the atomic number

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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

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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

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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

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Incorrect

True or False: The number of electrons in an atom is always equal to the number of protons.

True

False

Correct!

References

Incorrect

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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