Page 251 - Science Course 1 (Book 1)

Mo6-L7b: What are Substances and Compounds?

Compound Element symbols have either one or two letters.
a substance containing atoms of two or more Temporary symbols have three letters.
different elements chemically bonded together.
Hydrogen
A compound is a molecule that contains at least two Gold
different elements. 1
H 79
1.01 Au
All compounds are molecules but not all molecules 196.97
are compounds.

Molecule Molecule Molecule Compound
and and
compound compound
Metals
Let’s Begin Nonmetals
Metalloids

What is a substance? Many chemical symbols are the Ununquadium
114
first letter of the element’s Uuq
A substance is matter with a composition that is name such as H for hydrogen. 289
always the same.
Some chemical symbols represent names.
A certain substance always contains the same For example Au is from aurum, Latin word for gold.
kinds of atoms in the same combination.
Recently discovered elements have temporary
three-letter symbols until they get official names.
Molecules of an Element For example, Uuq is the symbol for element 114,
ununquadium. The unusual names are based on a
system of word parts. Un-un-quad-ium stands for
H H O O N N Cl Cl 1-1-4.

H2 O2 N2 Cl2
hydrogen oxygen nitrogen chlorine Key Concept
What are Substances and Compounds?

Molecules of a Compound What are atoms and elements related?

O N C
N O H H O O O O
NO H2O NO2 CO2
nitrogen water nitrogen carbon
oxide dioxide dioxide

An element is a
substance made of
only one kind of atom. GOLD
(Au)
For example, the element
gold is made of only
gold atoms, and all gold
atoms are alike.
Salt
Sodium chloride (salt) is (NaCl)
also a substance.

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