history of the periodic table · §created a table where elements with similar properties were...
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HISTORY OF THE PERIODIC TABLE
MENDELEEV & CHEMICAL PERIODICITY
Dimitri Mendeleev§ Russian chemist§ Hoped to organize elements according to
their properties§ Noticed when elements were arranged in
order by increasing atomic mass, certain similarities in chemical properties appeared at regular intervals
§ Created a table where elements with similar properties were grouped together§ Several empty spaces in his periodic table§ Predicted the existence and properties of
elements that would fill three of these spaces (1871)§ All three elements discovered by 1886
§ Scandium, Sc§ Gallium, Ga§ Germanium, Ge
§ Mendeleev’s fame came from his ability to predict the properties of the missing elements
§ Periodic law: the physical and chemical properties of the elements are periodic functions of their atomic numbers
MOSELEY AND THE PERIODIC LAW
Henry Moseley (1911)§ English scientist§ Discovered that elements fit into patterns
better when arranged in increasing order to nuclear charge (the number of protons!)
§ Led to the modern definition of atomic number and recognition that atomic number is the basis for organization of the periodic table
§ Periodic table: an arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column, or group
§ Three sets of elements added to the periodic table after Mendeleev’s time§ The noble gases§ The lanthanides§ The actinides
THE MODERN PERIODIC TABLE
The Noble Gases§ Nonflammable, colorless and
odorless gases§ All rather unreactive elements
due to the maximum number of electrons in their outermost shell
The Lanthanides§ Lanthanides: the 14 elements
with atomic numbers from 58 (cerium, Ce) to 71 (lutetium, Lu)
The Actinides§ Actinides: the 14 elements with
atomic numbers from 90 (thorium, Th) to 103 (lawrencium, Lr)
PERIODICITY
§ Can be observed in any group of elements in the periodic table
§ Reason for periodicity explained by the arrangement of the electrons around a nucleus
ORGANIZATION OF THE ELEMENTS
PERIODS & BLOCKS OF THE PERIODIC TABLE
§ Group: a vertical column of elements in the periodic table§ Tells how many electrons are in the
atom’s outer shell (valence electrons)
§ Period: a horizontal row of elements in the periodic table§ Length of each period is determined by
the number of electrons that occupy the energy sublevels being filled
Relationship Between Period Length & Sublevels Being Filled
Period Number
Number of Elements in
Period
Sublevels in order of filling
1 2 1s
2 8 2s2p
3 8 3s3p
4 18 4s3d4p
5 18 5s4d5p
6 32 6s4f5d6p
7 32 7s5f6d,etc
§ Period of an element can be determined from the element’s electron configuration
§ Periodic table can be divided into four sublevel blocks based on the electron configuration of elements – s, p, d, and f blocks
GROUPS 1 & 2: THE S-BLOCK
§ Elements of the s-block are chemically reactive metals
§ Hydrogen and helium do not share the same properties of Group 1 and 2
Elements of Group 1:§ Known as the alkali metals
§ Lose their one valence electron to form ions with a +1 charge
§ Properties: § Silvery appearance and soft enough to cut with a
knife (in its pure state)
§ Highly reactive§ Combine strongly with most nonmetals
Elements of Group 2:§ Known as the alkaline-earth metals
§ May lose their 2 valence electrons to form ions with a +2 charge
§ Properties:§ Metals are harder, denser, and stronger
than alkali metals§ Higher melting points§ Highly reactive
Alk
ali M
etal
s
Alk
alin
e-ea
rth M
etal
s
Transition Metals Nob
le G
ases
Halo
gens
Metalloids
Lanthanides
ActinidesInner-transition Metals
take out the periodic table graphic organizer passed out to you J
S
Alka
li Meta
ls
Alka
line-
earth
Meta
ls
GROUPS 3 – 12: THE D-BLOCK
§ Transition metals: metals with typical metallic properties in the d-block of the periodic table§ Special because they can form at least 2 different colored ions§ Valence electrons are found in more than one shell which causes
them to have more than one charge (oxidation state)§ Properties:
§ Good conductors of electricity§ High luster§ Less reactive than alkali and alkaline-earth metals§ Some so unreactive they do not form compounds easily
S
Alka
li Met
als
Alka
line-
earth
Met
als d
Transition Metals
§ Properties of the elements of the p-block vary greatly§ Includes:
§ all of the nonmetals except hydrogen and helium§ all six of the metalloids (semiconducting metals) § the halogens§ the noble gases
GROUPS 13-18: THE P-BLOCK
S
Alka
li Met
als
Alka
line-
earth
Met
als d
Transition Metals
p
Nobl
e Gas
es
Halo
gensMetalloids
S
Alka
li Met
als
Alka
line-
earth
Met
als d
Transition Metals
p
Nobl
e Gas
es
Halo
gensMetalloids
METALSElements to the left of the staircase are Elements to the right are
NON-METALS
§ Main-group elements: elements of the p-block together with elements of the s-block
LANTHANIDES & ACTINIDES: THE F-BLOCK
§ Also known as the inner-transition metals
§ Electrons fill the 4f sublevel§ Lanthanides are shiny metals similar to the
Group 2 alkaline-earth metals§ Actinides are all radioactive
§ The first 4 have been found naturally and the remaining are known lab-made elements
S
Alka
li Met
als
Alka
line-
earth
Met
als d
Transition Metals
p
Nobl
e Gas
es
Halo
gensMetalloids
f Lanthanides
ActinidesInner-transition Metals
Use a periodic table and choose two elements
§ In at least 10 sentences, explain the similarities and differences between the two elements that you have selected.
§ Make sure you at least include the following:§ Group/family§ Period§ Number of protons§ Number of neutrons§ Number of electrons§ Energy levels