Chapter 5: The Periodic Table
How are videos organized in a video store?
-books in a bookstore?
-food in a grocery store?
As the number of elements discovered grew over time, the need to
organize them into groups based on their properties also grew.
-in 1750, only 17 elements were known
-by the 1860s, 63 elements were known
-presently, at least 118 elements have been identified or created
(only 90 are found in nature)
A Russian chemist and teacher, Dmitri Mendeleev, came up with a
scheme for organizing the elements while playing solitaire, a game
that involves placing cards in columns according to similar properties
Mendeleev arranged the elements by increasing mass and how they behaved
when combined with hydrogen and oxygen
-by breaking the list into rows, a pattern emerged where columns contained
elements that increased in mass from top to bottom and which all had
similar properties with respect to chemical reactions
-this was an example of a periodic table, an arrangement of elements in
columns, based on a set of properties that repeat from row to row.
-spaces were left in the table for elements not yet discovered
Section 5.2 The Modern Periodic Table
Who is familiar with the terms:
-period
-group
-metal
-nonmetal
-metalloid
-transition metals
-periodic law
Period: each row of the periodic table
-period 1-2 elements
-period 2&3-8 elements
-period 4&5-18 elements
-period 6-32 elements
Group: each column of the periodic table
-elements in groups have similar electron configurations
-the electron configuration of an element determines its chemical properties
-therefore, elements in groups have similar chemical properties
The pattern of repeating properties in elements as a result of arranging them in
order of increasing atomic number in the periodic table is called the periodic law
Four pieces of information are usually displayed in the period table
1. Name of the element
2. Element's symbol
3. Atomic number
4. Atomic mass (the standard is 1 atomic mass unit = 1/12th the mass of a
carbon-12 atom)
Classes of Elements
There are 3 ways of classifying elements:
1. Whether they are solid, liquid, or gas at room temperature
2. Whether they occur naturally on Earth or not (all but 2 for #s 1-92 occur
naturally)
3. Placed in categories according to similar properties
a. Metals (on the left side of table)
b. Nonmetals (on the right side of table)
c. Metalloids (in-between)
A. Metals
-the majority of elements are classified as metals
-metals are solids at room temperature except for mercury
-metals are good conductors of heat and electricity
-most metals are malleable
-many metals are ductile (able to be stretched into thin wires)
-some metals are extremely reactive and some aren't (gold doesn't
react with oxygen, but magnesium does)
Transition Metals
Watch potassium react with water!
-bridge the elements on the left and right sides of the periodic table
-many form compounds with distinctive colors (p. 137 in textbook)
-some are very similar (lanthanide and actinide series)
B. Nonmetals
-poor conductors of heat and electricity
-many are gases at room temperature because they have low boiling points
-nonmetals that are solid at room temperature are brittle
-some are very reactive, like flourine, and some hardly reactive at all, like
group 8 elements (very diverse properties)
C. Metalloids
-have properties that fall between metals and nonmetals
-ability to conduct electricity varies with temperature
Patterns across a period
-elements become more nonmetallic from left to right
-most reactive metals are on left
-most reactive nonmetals are on right (group 7)
Patterns down a family
-most reactive metals are towards the bottom
-most reactive nonmetals are towards the top
Alkali Metals
1A
8A
2A
3A 4A 5A 6A 7A
Alkaline Earth Metals
1A
8A
2A
3A 4A 5A 6A 7A
Boron Family
1A
2A
8A
3A 4A 5A 6A 7A
Carbon Family
1A
2A
8A
3A 4A 5A 6A 7A
Nitrogen Family
1A
2A
3A 4A 5A 6A 7A
8A
Oxygen Family
1A
2A
3A 4A 5A 6A 7A
8A
Halogen Family
1A
2A
3A 4A 5A 6A 7A
8A
Noble Gases
1A
8A
2A
3A 4A 5A 6A 7A
5.3: Families of the Periodic Table
- Electrons in the outermost energy level of an atom are called
valence electrons.
- These electrons determine how an element reacts, and
therefore, its chemical properties.
Draw the Bohr model for Beryllium, Magnesium and Calcium:
What is similar about each?
Be
4 p+
5 no
Mg
12 p+
12 no
Ca
20 p+
20 no
5.3: Families of the Periodic Table
Without actually making the Bohr model, find the
number of valence electrons of the following
elements:
Helium
Arsenic
Potassium
Carbon
Iodine
Aluminum
Argon
5.3: Families of the
On pages 191 & 192 of your FCP workbook is an
Alien Periodic table. This is a periodic table of the
elements as discovered on a distant planet with
intelligent life. (For some reason, these aliens use our
alphabet, but that's another matter) Your job is to
read the clues for what elements the aliens are
referring to on our periodic table, and fill in the blank
periodic table on page 192 with their symbols for the
elements. It will seem confusing at first and that's ok.
If a clue doesn't help you right away, go on to the
next clue.