Section 3
Representative Groups
Key Concepts
• Why do the elements in a group have
similar properties?
• What are some properties of the A groups
in the periodic table?
Valence Electrons
• A valence electron is an electron that is in
the highest occupied energy level of an
atom.
• Elements in a group have similar
properties because they have the same
number of valence electrons.
• These properties will not be identical
because the valence electrons are in
different energy levels.
Family 1 – The Alkali Metals
The Alkali Metals
• One valence electron in the outermost
energy level
• Tend to lose the electron
• True metals
• Very reactive, never found un-reacted in
nature
• Not many uses, but their compounds
are needed for life
• Ex. NaCl
3
Li
Lithium
11
Na
Sodium
19
K
Potassium
37
Rb
Rubidium
55
Cs
Cesium
87
Fr
Francium
Family 2 – Alkaline Earth Metals
Alkaline Earth Metals
• Two valence electrons in their
outermost energy level
• Tend to lose these electrons (true
metals)
• Very reactive, never found un-reacted
in nature (not as reactive as Alkali
Metals because these have to lose two
electrons)
• The compounds of these metals are
very important
• Ex. Calcium compounds
4
Be
Beryllium
12
Mg
Magnesium
20
Ca
Calcium
38
Sr
Strontium
56
Ba
Barium
88
Ra
Radium
Transition Metals
Transition Metals
•
•
•
•
•
Most have 1 or 2 valence electrons
Properties similar to other metals
Can share electrons as well as give them
Usually bright colors (used in paints)
Ex, Iron, Copper, Silver, Gold
Boron Family
Boron Family
• 3 valence electrons
• Boron is a metalloid all others are
metals
• Many uses for these elements
• Aluminum is the most abundant
metal in Earth’s crust.
5
B
Boron
13
Al
Aluminum
31
Ga
Gallium
49
In
Indium
81
Tl
Thallium
Carbon Family
Carbon Family
• 4 valence electrons
• Can either give or take 4 electrons or
share electrons
• Can form millions of different
compounds
• Carbon is a nonmetal, Silicon and
Germanium are metalloids, the rest are
metals
• Except for water, most of the
compounds in your body contain
carbon.
6
C
Carbon
14
Si
Silicon
32
Ge
Germanium
50
Sn
Tin
82
Pb
Lead
Nitrogen Family
Nitrogen Family
• 5 valence electrons
• Tend to share electrons when bonding
• N and P are nonmetals, As and Sb are
metalloids, and Bi is a metal
• Besides nitrogen, fertilizers often
contain phosphorus.
7
N
Nitrogen
15
P
Phosphorus
33
As
Arsenic
51
Sb
Antimony
83
Bi
Bismuth
Oxygen Family
Oxygen Family
• 6 valence electrons
• Most share electrons in bonding
• O, S, and Se are nonmetals, Te and
Po are metalloids
• Oxygen is the most abundant
element in Earth’s crust.
8
O
Oxygen
16
S
Sulfur
34
Se
Selenium
52
Te
Tellurium
84
Po
Polonium
Family 17 - Halogens
Halogens
• 7 valence electrons
• Most reactive nonmetals
• Need to gain only one electron to fill their
outermost energy level
• Never found un-reactive in nature
• F most reactive nonmetal
• Fluorine and chlorine are gases, bromine is a
liquid that evaporates quickly, and iodine is a
solid that sublimes.
• Despite their physical differences, the
halogens have similar chemical properties
9
F
Fluorine
17
Cl
Chlorine
35
Br
Bromine
53
I
Iodine
85
At
Astatine
Family 18 – Noble Gases
Noble Gases
• The noble gases are colorless and
odorless and extremely unreactive.
Non-reactive gases
• Have a full outer energy level
• Most all other elements try to get their
outer energy level to look like Noble
Gases
• They need to bond with other elements
to achieve this
2
He
Helium
10
Ne
Neon
18
Ar
Argon
36
Kr
Krypton
54
Xe
Xenon
86
Rn
Radon
Reviewing Concepts
• 1. Explain why elements in a group have similar
properties.
• 2. What is the relationship between an alkali
metal’s location in Group 1A and its reactivity?
• 3. What element exists in almost every
compound in your body?
• 4. Which Group 5A elements are found in
fertilizer?
• 5. Which group of elements is the least reactive?
• 6. Why is hydrogen located in a group with
reactive metals?