Transcript Periodic Table of Elements

Elements in Ancient and Medieval Times
Dalton’s elements (1809)
Periodic Table of Elements - History
During the nineteenth century, chemists began to categorize the
elements according to similarities in their physical and chemical
properties. The end result of these studies was our modern periodic
table.
In 1829, J. Doebereiner classified some elements into
groups of three, which he called triads. The elements
in a triad had similar chemical properties and orderly
physical properties (MODEL OF TRIADS): [Cl2, Br2,
I2], [P, As, Sb], [Li, Na, K] and [Ca, Sr, Ba].
In 1863, J. Newlands suggested that elements
may be arranged in “octaves” because he noticed
(after arranging the elements in order of
increasing atomic mass) that certain properties
repeated every 8th element (LAW OF OCTAVES).
Johann Doebereiner
John Newlands
Telluric Helix of Screw (A. de Chancourtois) (1862)
A. de Chancourtois
Periodic Table of Elements - History
In 1869 Dmitri Mendeleev published a table of
the elements organized by increasing atomic
mass.
At the same time, Lothar Meyer published his
own table of the elements organized by
increasing atomic mass,
Dmitri Mendeleev
Both Mendeleev and Meyer arranged the elements
in order of increasing atomic mass. Both left
vacant spaces where unknown elements should fit.
So why is Mendeleev called the “father of the
modern periodic table” and not Meyer, or both?
Lothar Meyer
Periodic Table of Elements - History
Mendeleev stated that if the
atomic weight of an element
caused it to be placed in the wrong
group, then the weight must be
wrong. (He corrected the atomic
masses of Be, In, and U).
He used the table to predict the
physical properties of three
elements that were yet unknown
(Sc, Ge, Ga, Tc).
When
properties
of
these
elements turned out to be very
close to the predicted ones by
Mendeleev, his table was widely
accepted.
Original Periodic Table of the Elements
Periodic Table of Elements - History
However, in spite of Mendeleev’s great achievement, problems
arose when new elements were discovered and more accurate
atomic weights determined.
By looking at our modern periodic table, can you identify what
problems might have caused chemists a headache?
Henry Moseley (1913)
rearranged the elements
in order of increasing
atomic number.
Ar and K
Co and Ni
Te and I
Th and Pa
Henry Moseley
Modern Periodic Table
of the Elements
Different modern versions of Periodic Table
Round Table of Elements
Fractal Table of Elements
Different modern versions of Periodic Table
Energetic blocks in Periodic Table
1s
2p
3d
2s
4s
3s
3p
Physical properties of elements
in the Periodic Table
17 nonmetals
7 metalloids
88 metals
Ionization energy
The ionization energy (EI) of an atom or molecule is the minimum
energy required to remove (to infinity) an electron from the atom or
molecule isolated in free space and in its ground electronic state.
Electronegativity in Periodic Table
Electronegativity, symbol χ (the Greek letter chi), is a chemical
property that describes the ability of an atom to attract electrons
towards itself.
Ed(AB) – dissociation energy (eV)
Atomic radius
• Van der Waals radius: half the minimum distance between the nuclei of two
atoms of the element that are not bound to the same molecule.
• Ionic radius: the radius of the ions deduced from the spacing of atomic nuclei in
crystalline salts that include that ion. The length of the ionic bond should equal the
sum of their ionic radii.
• Covalent radius: the radius of the atoms of an element when covalently bound
to other atoms, as deduced the separation between the atomic nuclei in molecules.
The length of a covalent bond should equal the sum of their covalent radii.
• Metallic radius: the radius of atoms of an element when joined to other atoms
by metallic bonds.
 Cations are smaller than corresponding atoms.
 Anions are larger than corresponding atoms.
II/
Due to increased attraction
Larger nuclear charge
II/
Factors affecting the atomic radius:
Melting point
Melting point for a solid is the temperature at which the solid and
liquid phases exist in equilibrium.
I
In
Rh
Nb
Rb
As
Cu
Mn
Sc
Cl
Al.
F
B
4500
4000
3500
3000
2500
2000
1500
1000
500
0
-500
H
Tmelt.[ºC]