Transcript The Periodic Table

The Periodic Table
Dmitri Mendeleev
Created a table arranged by increasing atomic mass and chemical
characteristics
Wrote the periodic law - Chemical physical properties of the elements are a
periodic function of their atomic mass.
Predicted the characteristic of three undiscovered elements, Germanium,
Gallium and Scandium



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1 2
3
9 10 11
17
19
25 26 27
4
20
28
5
13
21
29
14
22
30
7
15
23
31
8
16
24
32
Mendeleev sorted the elements by similar properties, and then by increasing
atomic mass.
So elements 1 , 9, 17, 25, all had similar properties. Each column or family had
Its own set of characteristics.
He saw that there should be an element with the weight of 12 and it should also
Have the characteristics of elements 4, 20, and 28.
Problems
 Not all the element fell into place as they
should, but it was the best table at the time.
Henry Moseley
 Found a way to count protons
 Then the table was then rearranged
according to increasing atomic number.
 ( # of protons)
 This removed the problems in Mendeleev’s
table.
How is the table arranged?
What are?
Metals
Nonmetals
Metalloids
Active metals
noble gases
Transition metals
Halogens
Alkali and alkaline earth metals
Atomic radius and how it varies
General pattern
Ionization and atomic size
 X + energy →
X+ + e-
 An ion is a charged particle ( positive or
negative)
 Anion = negative
cation = positive
 The energy required to make a + ion is
called ionization energy.
 The smaller the atomic radius the harder it is
to remove an electron. ( explain)
 Electrons (-) closer to the nucleus(+) are
held more strongly.
 Pattern on the table, as you move down a
family ionization energy gets lower.
 As you move left to right ionization energy
gets higher.
Ionization energy
Successive ionization energy
 It is all ways harder to remove the second
and third electron , do to the fact the same
number of protons is now holding fewer and
fewer electrons.
 And some times messing with a more stable
electron configuration.
Atomic radius verse ionic radius
 + ions are smaller than their parent atom
 - ions are larger than their parent atom.
Why? Its related to the number of protons
and electrons present.
Atomic and ionic radii
Electronegativity
 The measure of an atoms attraction for a
shared electron.
 Similar to ionization energy, it is still a
measure of an atoms attraction for
electrons.
 Pattern on the table is the same.
Electron affinity
 The energy released when an atom gains
an electron.
 X + e- → X- + energy
 Opposite of ionization energy