Chemistry Reference
In-Depth Information
3.
The atomic mass unit (u) is based on an atom of the isotope
_______________.
4.
The _______________ number of an atom is equal to the number of
protons it has.
5.
The _______________ number of an atom is equal to the total
number of protons and neutrons in its nucleus.
6.
Atoms of the same element with differing masses are called
_______________.
Lesson 3-2: Elemental Symbols
In Chapter 5 we will go over chemical formulas, which are really the
“words” that make up the language of chemistry. The elemental symbols,
which are shown on the Periodic Table of Elements, are the letters that
make up the (words) chemical formulas. Chemical formulas combine in
chemical equations to form the “sentences” in the language of chemistry.
Before you can be expected to correctly write the chemical equations (sen-
tences) or the chemical formulas (words), you must make sure that you are
using the elemental symbols (letters) correctly.
One chemical equation that you may be familiar with, from your biol-
ogy studies, is the equation for photosynthesis, shown here:
6CO
2
+ 6H
2
O
C
6
H
12
O
6
+ 6O
2
The entire statement represents the chemical equation. The chemical
equation is made up of four chemical formulas: CO
2
, H
2
O, C
6
H
12
O
6
, and
O
2
. These chemical formulas are made up of either one, two, or three el-
emental symbols. For example, C
6
H
12
O
6
is made up of three elemental sym-
bols (C, H, and O).
Really, the only “trick” to working with elemental symbols is to be care-
ful to distinguish between uppercase and lowercase letters. There is actu-
ally a huge difference between the substances shown in the formulas “CO”
and “Co.” CO is the chemical formula for the compound known as carbon
monoxide, which is a colorless, poisonous gas. Co is the elemental symbol
for the element cobalt, which is a metal. Remember: Regardless of how
many letters are used to represent an element, each elemental symbol can
only contain a single capital letter. The elemental symbols for some of the
elements that your instructor will likely discuss most often are shown in
Figure 3-2a.
