Elements, Atoms, and Molecules
Elements are substances that cannot be separated into simpler substances. Salt is made up
of the elements sodium and chloride. Water is made up of the elements hydrogen and
oxygen.
The smallest particles of matter are called atoms. Remember the carrot from the other
chapter. If you continue to chop a carrot into smaller and smaller pieces, eventually you
would reach a point where you could not cut up the carrot anymore, but still have carrot. You would then have
molecules of carrot. The same applies to elements. If you continually cut up a piece of aluminum, you will
reach a point that you could no longer divide it. These are aluminum atoms. An atom is the smallest particle of
an element that has the properties of that element. Some properties of aluminum are: shiny, silver colored,
fragile, and thin. Each element has its own type of properties.
Chemists use symbols to represent elements. A symbol is a letter or picture
used to represent something. Chemists use one or two lettters to represent
elements. The symbol for aluminum is Al. The symbol for oxygen is O.
A model of an oxygen
molecule.
The symbol for oxygen is O. "O" stands for one atom of oxygen. Oxygen
stoms are joined in pairs. To write a pair of oxygen atoms using symbols,
we use the symbol O and the number 2. Oxygen would be (O2). The 2 is a
subscript. "Sub" means "below". The 2 is written to the right of and below
the O. A pair of oxygen atoms is a molecule of oxygen. A molecule is the
general term used to describe atoms connected by chemical bonds. Molecules of most elements are made up of
only one of atom of that element. Oxygen, along with nitrogen, hydrogen, and chlorine are made up of two
atoms. Look at the model of oxygen above. The two balls represents the two oxygen molecules. The oxygen
molecules are bonded or stuck together. We will learn about bonds later.
Compounds
A compound is a substance formed when two or more elements are chemically joined. Water, salt, and sugar are
examples of compounds. When the elements are joined, the atoms lose their individual properties and have
different properties from the elements they are composed of. A chemical formula is used a quick way to show
the composition of compounds. Letters, numbers, and symbols are used to represent elements and the number of
elements in each compound.
Mixtures
Mixtures are two or more substances that are mixed together but not chemically joined. A good example of a
mixture is a salad. There are tomatoes, lettuce, cucumbers, and salad dressing all mixed together. No chemical
reactions occur between the vegetables and the dressing. You can separate each of the vegetables from each
other. When spices are added to a cake before baking, do you think they form compounds or mixtures? Why?
www.nyu.edu/pages/mathmol/textbook/compounds.html
and
chem4kids.com
Name: ______________________________________________
Date: ____________
E# ________
The Makeup of Matter: www.youtube.com/watch?v=cV4jJZCIMPo
Follow up: www.youtube.com/watch?v=AfXxZwNLvPA
Atom: “That which cannot be cut/indivisible”
1) What is an atom?
2) What is meant by a “pure substance”?
3) How does an atom compare to an element?
4) Are atoms made up of elements?
5) Are elements made up of atoms
YES
YES
NO
NO
6) How many different elements are there?
7) What makes something a molecule?
8) What makes something a compound?
9) How is a compound different than a mixture?
10) Are compounds made up of molecules?
YES
NO
11) Are molecules made up of compounds?
YES
NO
SUMMARY
When matter is made of only ONE kind of atom, it is called a(n) ________________________.
When matter is a combination of two or more kinds of atoms, it is called a(n) _______________
When matter is a combination of two or more kinds of elements, it is called a(n) _________________
Name: ______________________________________________
Date: ____________
E# ________
The Makeup of Matter: www.youtube.com/watch?v=cV4jJZCIMPo
Follow up: www.youtube.com/watch?v=AfXxZwNLvPA
Atom: “That which cannot be cut/indivisible”
1) What is an atom?
Smallest particle of all matter
2) What is meant by a “pure substance”
Substance only contains ONE kind of particle
3) How does an atom compare to an element?
All elements are made up of the SAME kind of atom
4) Are atoms made up of elements?
YES
NO
5) Are elements made up of atoms
YES
NO
6) How many different elements are there?
116-117
7) What makes something a molecule?
Two or more atoms CHEMICALLY combined
8) What makes something a compound?
A substance made of two or more elements.
9) How is a compound different than a mixture?
A compound is formed when elements chemically combine. Compound have new properties
from original substances. Mixture contains unique elements or molecules that still have their
original properties. The elements and molecules can be separated (like salt from water)
10) Are compounds made up of molecules?
YES
NO
11) Are molecules made up of compounds?
YES
NO
SUMMARY
When matter is made of only ONE kind of atom, it is called a(n) _________element.
When matter is a combination of two or more kinds of atoms, it is called a(n) ________ molecule
When matter is a combination of two or more kinds of elements, it is called a(n) _____Compound