Download intro to atoms, elements, compounds, etc

CLASS NOTES: INTRODUCTION TO
ATOMS, ELEMENTS, COMPOUNDS, ETC.
A
***The following definitions are very important to know (MCAS!), and are
frequently confuse students – be sure to know them!!!***
1. ATOMS:
are the smallest whole units of matter – often called the “building blocks” of objects or
materials. In other words, atoms are the smallest parts that make up any substance,
chemical, or object.
2. ELEMENTS:
are ATOMS of a particular type. Carbon, Gold, Oxygen, and Hydrogen are all examples of
ELEMENTS- each is a different type of atom. Each ELEMENT has its own particular # of
protons in its nucleus – called its ATOMIC NUMBER.
3. MOLECULES : are the smallest “parts” of a substance that still retain the properties of the
substance. For example, imagine that you have 4 water molecules in your hand:
H2 0
H2 0
H2 0
H2 0
(still water)
H2 0
H2 0
(still water)
H2 0
H2
Hydrogen
gas
still water
0
one oxygen
atom
NO LONGER WATER!!!
So, if you separate the 2 hydrogen atoms from the oxygen atom, you no longer have one
substance that behaves like water, but two substances that behave like a gas.
Molecules are groups of atoms that combine to form a substance or chemical.
For example, “H2O” is a MOLECULE of water – 2 HYDROGEN atoms & 1 OXYGEN atom
combine to form a new substance with its own properties, properties that are
different from those of the atoms that make it up.
To explain further, both hydrogen and oxygen alone make up gases, but when they combine
to form water, one water MOLECULE behaves as a liquid.
Other examples of MOLECULES include O2 (oxygen gas), C02 (carbon dioxide),
and C6H12O6 (glucose)
4. *TYPES OF MOLECULES:
A. COMPOUNDS: are MOLECULES that consist of 2 or more different types of atoms;
that is, they consist of 2 or more ELEMENTS.
**MOLECULES that are made of only 1 element, or 1 type of atom, ARE NOT
COMPOUNDS!!!!**
EXAMPLES OF COMPOUNDS:
1. H20 – CONSISTS OF HYDROGEN AND OXYGEN
2. CO2 – CONSISTS OF CARBON AND OXYGEN
DIATOMIC COMPOUNDS: consist of 2 TOTAL atoms, and of more than one element: CO, NaCl, etc.
TRIATOMIC COMPOUNDS: consist of 3 TOTAL atoms, and of more than one element: CO2, H2O, etc.
B. DIATOMIC and TRIATOMIC ELEMENTS: are MOLECULES that consist of ONLY ONE
type of atom; that is, they consist of ONLY ONE ELEMENT.
EXAMPLES:
1. DIATOMIC ELEMENTS: N2, 02 – CONSISTS OF 2 ATOMS OF THE SAME ELEMENT
2. TRIATOMIC ELEMENTS: 03 – CONSISTS OF 3 ATOMS OF THE SAME ELEMENT
*3. MONATOMIC ELEMENTS: He, Ne, Kr – CONSIST OF 1 ATOM OF THE SAME ELEMENT –
are technically NOT MOLECULES, as they consist of only one atom
5. PURE SUBSTANCES:
are substances or materials that consist of only ONE TYPE OF MOLECULE.
For example:
AIR is NOT a pure substance – it consists of N2, O2 , CO2 – which are SEVERAL DIFFERENT TYPES OF
MOLECULES
BOTTLED OXYGEN IS a pure substance – it consists ONLY of O2, and NO OTHER TYPES OF
MOLECULES
6. MIXTURES:
are substances or materials that consist of MORE THAN ONE TYPE OF
MOLECULE.
For example:
AIR is a MIXTURE – it consists of N2, O2 , CO2 – which are SEVERAL DIFFERENT
TYPES OF MOLECULES
MOLECULES, COMPOUNDS, MIXTURES, AND PURE SUBSTANCES
KEY:
= ONE HYDROGEN
ATOM
= ONE OXYGEN
ATOM
= ONE NITROGEN
ATOM
THIS DIAGRAM REPRESENTS THE FOLLOWING:
1. TWO MOLECULES OF NITROGEN GAS (N2)
2. A PURE SUBSTANCE: ONLY N2 MOLECULES ARE PRESENT
THIS DIAGRAM DOES NOT REPRESENT:
1. ANY COMPOUNDS: ONLY ONE ELEMENT (N) IS PRESENT IN EACH
MOLECULE
2. A MIXTURE: ONLY ONE SUBSTANCE (NITROGEN GAS) IS PRESENT.
THIS DIAGRAM REPRESENTS THE FOLLOWING:
1. THREE MOLECULES OF WATER (H2O)
2. A PURE SUBSTANCE: ONLY H2O MOLECULES ARE PRESENT
3. COMPOUNDS: TWO ELEMENTS (H & O) ARE PRESENT IN
EACH MOLECULE
THIS DIAGRAM DOES NOT REPRESENT:
2. A MIXTURE: ONLY ONE TYPE OF MOLECULE IS PRESENT.
***NOTICE: A PURE SUBSTANCE CAN BE MADE OF
COMPOUNDS!!!***
THIS DIAGRAM REPRESENTS THE FOLLOWING:
1.TWO MOLECULES OF WATER (H2O) AND
TWO MOLECULES OF NITROGEN GAS (N2)
2. A MIXTURE: TWO DIFFERENT TYPES OF MOLECULES
(H20 & N2) ARE PRESENT.
3. ONE TYPE OF COMPOUND: WATER: TWO ELEMENTS
(H & O) ARE PRESENT; NITROGEN GAS IS NOT A
COMPOUND
THIS DIAGRAM DOES NOT REPRESENT:
1. A PURE SUBSTANCE: MORE THAN ONE TYPE OF
MOLECULE IS PRESENT (H20 & N2)