The Periodic Table
Now that we know where (or approximately where) to find the
parts of atoms, we can start to understand how these factors all
come together to affect how we view the elements.
We can look at them as individual yet interacting chemicals, and
we are able to group them based, not only on the properties
they present when in isolation, but also the properties they reveal
when exposed to other elements or compounds.
History of the Periodic Table
Dmitri Mendeleev, building on the ideas from chemists before
him, developed the modern periodic table.
He argued that element properties are periodic functions of their
atomic weights. We now know that element properties are
periodic functions of their atomic number. By elemental
properties, we are describing both physical and chemical
properties.
Atoms are listed on the periodic table in rows, based on number of
protons.
Information on the Periodic Table
A periodic table usually has the following information:
Name of Atom
Element Symbol - the one or two letters designating the
atom
Atomic Number - the number of protons in that particular atom
Atomic Mass - the average atomic mass for that atom
NOTE: A periodic table may have more information or
less information, depending on the publisher and intended use.
Periodic Table
The periodic table is made of rows and columns:
Rows in the periodic table are called Periods.
Columns in the periodic table are called Groups.
Groups are sometimes referred to as Families, but "groups" is more traditional.
groups
1
periods
2
3
4
5
6
*
**
7
6
7
*
**
Periodic Table
The periodic table is "periodic" because of certain trends that are seen in the elements.
Properties of elements are functions of their atomic number.
Elements from the same group have similar physical and chemical properties.
Atoms are listed on the periodic table in rows, based on number of protons, which is equal to the
number of electrons in a neutral atom.
[ ]
1
What is the atomic number for the element in period 3, group 16?
2
What is the atomic number for the element in period 5, group 3?
Special Groups
Noble Gases
Halogens
Transition Metals
Chalcogens
Alkaline Earth Metals
Alkali Metals
Some groups have distinctive properties and are
given special names.
Groups of Elements
Enjoy Tom Lehrer's
Famous Element Song!
Alkali Metals
Group 1 Alkali Metals (very reactive metals)
Alkaline Earth Metals
Group 2 Alkaline Earth Metals (reactive metals)
Groups 3 - 12 Transition Metals (low reactivity, typical metals)
Transition Metals
Chalcogens
Group 16 Chalcogens (elements of fire)
Halogens (highly reactive, nonmetals)
Halogens
Group 17
Noble Gases
Group 18 Noble Gases (nearly inert)
Alkaline Earth
Metals
Alkali Metals
Noble Gases
Halogens
Chalcogens
Transition Metals
Metals, Nonmetals, and Metalloids
The periodic table can be also divided into metals (blue) and
nonmetals (yellow) . A few elements retain some of the properties of
metals and nonmetals, they are called metalloids (pink).
metals
B
nonmetals
Si
Ge
As
Sb
Te
?
Diatomic Elements
Seven elements in the periodic table are always diatomic.
In elemental form, they are always seen as two atoms bonded together.
H2, O2, N2, Cl2, Br2, I2, F2
H
N O
F
Cl
Br
I
. . . we now know that elements in the same family
have very similar electron configurations
Noble Gases
Halogens
Transition Metals
Chalcogens
Alkaline Earth Metals
Since the families are based
on reactivates, and next,
how something reacts is
based off of how its
electrons are arranged. . .
Alkali Metals
Electron Configuration
Group names
Noble Gases - Group 18, s2p6 ending
Have a full outermost shell
Halogens - Group 17, s2p5 ending
Highly reactive, need one electron to have a full outer shell.
Alkali Metals - Group 1, s1 ending
Very reactive
Alkaline Earth Metals - Group 2, s2 ending
Reactive
Transition Metals (d-block) - Groups 3 - 12
somewhat reactive, typical metals, ns2, (n-1)d ending
Inner transition metals ( f -block) - the bottom two rows
somewhat reactive and radioactive, ns2, (n-2)f ending
3
The elements in the periodic table that have completely filled
shells or subshells are referred to as:
A
noble gases.
B
halogens.
C
alkali metals.
D
transition elements.
E
I don't know how to answer this.
4
The elements in the periodic table which lack one electron from a filled
shell are referred to as:
A
noble gases.
B
halogens.
C
alkali metals.
D
transition elements.
E
I don't know how to answer this.
5
The elements in the periodic table which have a single outer s
electron are referred to as:
A
noble gases.
B
halogens.
C
alkali metals.
D
transition elements.
E
I don't know how to answer this.
Looking back at the Periodic Table of the Elements
Atoms with the same number of electrons in their outer shells or same outer
electron configuration, have similar chemical behavior. They appear in the
same column of the periodic table.
The periodic table of elements can be grouped into blocks based on electron
configuration of the atoms. s, p, d, and f blocks will have the last electron in the
atom filling into these sub shells respectively.
The elements with configuration - full or half full in their outer sub shell are the
most distinctive.
Stability
When the elements were studied it was notices that some of them do not react in certain situations in which
others do. These elements were labeled "stable" because they did not change easily. When these stable
elements were grouped together, it was noticed that periodically, there were patterns in the occurrence of
stable elements.
Today we recognize that this difference in stability is due to electron configurations.
Group Numbers
1
2A
2
8A
18
8B
3B 4B 5B 6B 7B
3 4 5 6 7 8
}
1A
3A 4A
5A 6A 7A
13 14 15 16 17
1B 2B
9 10 11 12
There are two methods for labeling the groups, the older method
shown in black on the top and the newer method shown in blue on the
bottom.
Stability
Elements of varying stability fall into one of 3 categories. The most stable atoms have completely full energy
levels.
~Full Energy Level
~Full Sublevel (s, p, d, f)
~Half Full Sublevel ( d5, f7)
1
2
3
4
5
6
7
6
7
Stability
Next in order of stability are elements with full sublevels.
~Full Energy Level
~Full Sublevel (s, p, d, f)
~Half Full Sublevel ( d5, f7)
1
2
3
4
5
6
7
6
7
Stability
Finally, the elements with half full sublevels are also stable, but not as stable as elements with fully energy
levels or sublevels.
~Full Energy Level
~Full Sublevel (s, p, d, f)
~Half Full Sublevel ( d5, f7)
1
2
3
4
5
6
7
6
7
Electron Configuration Exceptions
You should know the basic exceptions in the d- and f-sublevels. These fall in the circled areas on
the table below.
1
2
3
4
5
6
7
6
7
Electron Configuration Exceptions
Chromium
Expect: [Ar] 4s2 3d4
Actually: [Ar] 4s1 3d5
Sometimes, in order to atleast get a half full d sublevel, some elements will cheat a bit and steal electrons
from an s sublevel. To see why this can happen we need to examine how "close" d and s sublevels are.
1
2
3
4
5
6
7
Cr
6
7
Energies of Orbitals
Its kind of like borrowing a cup of
sugar from a neighbor. You'd only
borrow it from someone you were
close to, and only if you needed it.
It's the same thing for electrons.
7f
7d
6f
7
6
7p
6d
5f
7s
6p
5d
Energy
Because of how close the f and d
orbitals are to the s orbitals en
electron can easily be taken from
the s orbital (leaving it half full) and
given to the f or d orbital, causing
them to also be half full.
5
4
4f
6s
5p
4d
5s
4p
3d
3
4s
3p
2
3s
2p
1
2s
1s
Electron Configuration Exceptions
Copper
Expect: [Ar] 4s2 3d9
Actually: [Ar] 4s1 3d10
Copper gains stability with a full d-sublevel by taking electrons
from the s orbital.
1
2
3
4
5
6
7
Cu
6
7
The Periodic Table
Now that we know where (or approximately where) to find the
parts of atoms, we can start to understand how these factors all
come together to affect how we view the elements.
We can look at them as individual yet interacting chemicals, and
we are able to group them based, not only on the properties
they present when in isolation, but also the properties they reveal
when exposed to other elements or compounds.
History of the Periodic Table
Dmitri Mendeleev, building on the ideas from chemists before
him, developed the modern periodic table.
He argued that element properties are periodic functions of their
atomic weights. We now know that element properties are
periodic functions of their atomic number. By elemental
properties, we are describing both physical and chemical
properties.
Atoms are listed on the periodic table in rows, based on number of
protons.
Information on the Periodic Table
A periodic table usually has the following information:
Name of Atom
Element Symbol - the one or two letters designating the
atom
Atomic Number - the number of protons in that particular atom
Atomic Mass - the average atomic mass for that atom
NOTE: A periodic table may have more information or
less information, depending on the publisher and intended use.
Periodic Table
The periodic table is made of rows and columns:
Rows in the periodic table are called Periods.
Columns in the periodic table are called Groups.
Groups are sometimes referred to as Families, but "groups" is more traditional.
groups
1
periods
2
3
4
5
6
*
**
7
6
7
*
**