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The Periodic Law

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This was incredibly important for the work that Dmitri ... In 1898, Ramsay discovered krypton and xenon. Friedrich Ernst Dorn discovered radon in 1900. ... – PowerPoint PPT presentation

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Title: The Periodic Law


1
Chapter 5
  • The Periodic Law

2
Section 5-1
  • History of the Periodic Table

3
Stanislao Cannizzaro13 Jul 1826 10 May 1910
4
Cannizzaro
  • Was the first scientist to accurately measure
    atomic masses.
  • This was incredibly important for the work that
    Dmitri Mendeleev was going to do.

5
Dmitri Mendeleev8 Feb 1834 2 Feb 1907
6
Dmitri Mendeleev
  • Arranged the elements on cards in order of
    increasing atomic mass
  • Found columns of elements with similar properties
  • There were gaps in his columns

7
Basic Version of Mendeleevs Periodic Table
8
The gaps
  • Hypothesized the gaps were undiscovered elements.
  • Predicted the props of these elements.
  • Predicted them well.

9
Mendeleevs Mistake
  • There were irregularities when arranged according
    to atomic weight.

10
Henry Mosely23 Nov 1887 10 Aug 1915
11
Henry Mosely
  • Discovered a unique charge on the nucleus of the
    atom.
  • Arranged the elements according to increasing
    atomic number
  • When he did this, the irregularities disappeared.

12
Periodic Law
  • The properties of elements tend to change with
    atomic number gradually, in a periodic way.

13
John Strutt 12 Nov 1842 30 Jun 1919William
Ramsay2 Oct 1852 23 Jul 1916
14
Strutt Ramsay
  • In 1894, they discovered argon.
  • Nobody noticed it before because it is completely
    unreactive.
  • In 1868, helium had been discovered as part of
    the sun and in 1895, Ramsay showed its existence
    on earth.
  • In 1898, Ramsay discovered krypton and xenon.
    Friedrich Ernst Dorn discovered radon in 1900.

15
Lanthanides
  • Discovered in the early 1900s.
  • They are found in the f block
  • They are shiny and act like the alkaline earth
    metals.

16
Actinides
  • All of these elements are radioactive.
  • They are found in the f block

17
Alkali Metals
  • Group 1
  • These elements are soft and can be cut with a
    knife.
  • They are highly reactive. The will react with
    both air and water.
  • They form alkaline/basic solutions (the opposite
    of acidic solutions).
  • Their electron configurations all end s1.

18
Sodium
19
Alkaline Earth Metals
  • Group 2 on the periodic table.
  • These elements are harder and denser than the
    alkali metals.
  • They are also reactive, but less so than the
    alkali metals.
  • They will also form alkaline/basic solutions.
  • Their electron configurations all end s2.

20
Magnesium
21
Hydrogen
  • This element doesnt belong with any group.
  • Its electron configuration is 1s1.

22
Helium
  • Even though its electron configuration ends s2,
    it isnt an alkaline earth metal. It is a noble
    gas because its highest energy level orbitals are
    full.

23
Transition metals
  • AKA transition elements
  • AKA d block elements
  • These elements are what we typically picture as
    common metals.
  • Their d orbitals are being filled.

24
Transition metals contd
  • They are shiny and good conductors of
    electricity.
  • They are less reactive than the other metals.
  • Some like gold are highly unreactive.

25
Chromium metal
26
Main Group Elements
  • Properties of these elements vary greatly because
    they include metals, nonmetals, metalloids, and
    noble gases.
  • They include the elements of the s and p blocks.
  • Sometimes they are called the representative
    elements because metals, nonmetals, metalloids,
    and noble gases are all represented

27
Halogens
  • These are the most reactive nonmetals.
  • They have 7 electrons in the outermost energy
    level and their electron configurations all end
    in s2p5.
  • They will react with metals to form salts.

28
Noble Gases
  • Group 18
  • No stable compounds for He, Ne, or Ar
  • Very low reactivity for the rest
  • Full s p orbitals (s2p6) in the higest energy
    level
  • This is very stable - they have no need to react
    with anything else.

29
Noble Gases contd
  • Most other atoms gain/lose e- to achieve this e-
    configuration
  • Ne Ar are used in signs
  • He - Low density - Air ships weather balloons

30
Noble Gases Contd
  • Rn - Radioactive
  • Found in homes - Linked to Lung CA
  • Once you test for it, you must disclose the
    results to potential buyers

31
5 3 Electron Configuration and Periodic
Properties
32
Atomic Radius
  • As you move down a group it increases
  • The outermost e- are being added to higher energy
    levels (further from the nucleus.

33
Atomic Radius
  • As you move across a period, it decreases
  • Even though e- are being added, they are added to
    the same energy level (same distance from the
    nucleus).

34
Atomic Radius
  • The charge on the nucleus increases as you move
    across the period and so it has a tighter hold
    on the e- being added.

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41
Shielding Effect
  • The reduction of the attractive force between a
    nucleus and its outer electrons due to the
    blocking effect of inner electrons.

42
Ionization Energy
  • The amount of energy needed to remove an electron
    from an atom

43
Ion
  • An atom that has gained or lost an e-
  • If it has gained an e-, it will be _____.
  • If it has lost an e-, it will be _____.

44
Ionization Energy
  • As you go down a group, it decreases
  • Shielding effect and electrons are being added to
    higher energy levels.

45
Ionization Energy
  • As you move across a period, it increases
  • The charge on the nucleus increases as you move
    across the period and so it has a tighter hold
    on the e- being added.

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51
Electron Affinity
  • Measures the tendency of an atom to attract
    electron
  • The energy change that occurs when an electron is
    acquired by a neutral atom.
  • Metals tend to have positive energy changes, they
    do not have a tendency to attract electrons
  • Non-metals tend to have negative energy changes,
    they have a strong tendency to attract electrons

52
EA
  • As you move down a group, electrons add with
    greater difficulty (values become more positive)
  • Shielding Effect and electrons are being added to
    higher energy levels.
  • There are exceptions

53
EA
  • Electrons add more easily as you move across the
    periodic table.(values become more neg)
  • The charge on the nucleus increases as you move
    across the period and so it has a tighter hold
    on the e- being added.

54
Electronegativity
  • Tendency for an atom to attract e- to itself when
    combined with another atom.
  • F is the most EN
  • EN decreases as you move down a group
  • EN increases as you move across a period

55
Electronegativity
  • Based on the Pauling Scale.
  • Linus Pauling
  • 28 Feb 1901
  • 19 Aug 1994

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