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Periodic Table Trends

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Title: Periodic Table Trends


1
Periodic Table - Trends
  • The Ultimate Cheat-Sheet
  • (if you know how to use it)

2
Atomic Radii
  • We must use an indirect method to measure the
    diameter of an atom
  • The atomic radius is one half of the distance
    between the nuclei of two atoms of the same
    element when the atoms are joined

3
Trends in Atomic Radii
4
In general, atomic size increases from top to
bottom within a group and decreases from left to
right across a period.
5
Ionization energy
  • The energy required to remove an electron from an
    atom is called ionization energy
  • The energy required to remove the first electron
    from an atom is called the first ionization
    energy, IE1
  • The energy to remove successive electrons is
    called IE2, IE3, etc.

6
Group Trends in Ionization Energy
  • State the trends in ionization energy
  • Which group has maxima?
  • Which group represents minima?
  • Account for these trends in terms of electron
    configurations

7
Group 8 The Noble Gases
  • These elements represent maxima because their
    outermost energy levels are filled

8
Group 1 The Alkali Metals
  • These elements represent minima because they all
    have one more electron than a noble gas.
  • This outermost electron starts a new energy level
  • lithium 1s2 2s1
  • sodium 1s2 2s2 2p6 3s1
  • potassium 1s2 2s2 2p6 3s2 3p6 4s1

9
Periodic Trends in Ionization Energy
  • The first ionization energy of representative
    elements tends to increase from left to right
    across a period
  • Nuclear charge increasesfrom left to right but
    theshielding effect remainsconstant
  • So, the attraction of the nucleus for an
    electron increases from left to right in a
    period

10
Trends in Ionization Energy
  • First ionization energy tends to decrease from
    top to bottom within a group and increase from
    left to right across a period

11
Ionization Energies for Successive Electrons
Note huge jumps in IE as we try to remove a core
electron - one from a filled lower energy level
12
Trends in Ionic Size
  • During reactions between metals and nonmetals
  • metal atoms tend to lose electrons
  • nonmetal atoms tend to gain electrons
  • This affects the size of the resulting ions
  • Cations are always smaller than the atoms from
    which they form
  • Anions are always larger than the atoms from
    which they form

13
Examples of Atomic vs. Ionic Size
14
Reactivity Within a Group
  • Increasing reactivity in Group 1
  • Li Na K Rb Cs
  • Two reasons
  • All tend to lose outer e
  • Larger atoms lose this valence electron more
    easily. Why?
  • Valence e is farther from nucleus

15
Reactivity Within a Group
  • Increasing reactivity in Group 7
  • F Cl Br I
  • Two reasons
  • All tend to gain an e to fill outer level
  • Smaller atoms fill outer level more easily. Why?
  • Valence electrons are closer to nucleus
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