Transcript The Periodic Table

The Periodic Table
Ch. 4
How are Elements Organized?
Section 4-1
John Newlands
• 1865 - Properties of the elements seemed to repeat every 8
elements
• Law of Octaves
Dmitiri Mendeleev
• Invented first
periodic table 1869
• In order by
chemical
properties
Mendeleev’s Periodic Table
• Predicted
undiscovered
elements
• Order did not fit
by atomic mass
Henry Moseley
• 1910 - Showed elements should ordered by atomic number
• Used the lines of x-ray spectra
The Periodic Law
Valence electrons
• Electrons in the
outer energy
level
• Determine the
chemical
properties
• The s and p
blocks are
predictable
Groups
• A vertical
column
• AKA
Families
• Horizontal Rows
• All elements in a row have the same
number of energy levels
Periods
Determine the period (energy level) and number of
valence electrons by the electron configuration
What elements
are we made of?
TOUR OF THE
PERIODIC TABLE
Section 4-2
The Main-Group Elements
• Elements in groups
1,2, and 13-18
• The s and p blocks
• # of valence
electrons
determined by
column
Alkali Metals
• Group 1, 1 valence
electron, very Reactive
• React with water to form
alkaline (basic) solutions.
(eg) Sodium Hydroxide
NaOH
Alkali Earth Metals
• Group 2,
also reactive
• 2 valence
electrons
• Calcium
Halogens
• Group 17, Very reactive
• 7 valence electrons
• “salt maker”, often react with
alkali metals to forms salts. NaCl
Noble Gases
• Group 18, far right
• Very stable, inert, non-reactive
because outer energy level is __
Hydrogen
• Simplest and most common
element in the universe
• Reacts with many other
elements
Metals
• Most are
shiny solids
• Ductile and
Malleable
• Good
conductors
of heat and
electricity
Metalloids
• Zig-zag
line
Transition Metals
• Groups 3-12,
the d block
elements
• Less reactive
Lanthanides and Actinides
• Fill f-orbitals
• Inner
transition
metals
Alloy
• A mixture of metals
• Has different, useful
properties
• Brass – copper and
zinc
• Steel – iron and carbon
TRENDS IN THE
PERIODIC TABLE
Section 4-3
Periodic
Trends
• A predicable change in a
particular direction
• Eg. The alkali metals are
more reactive the farther
down you go
• Trends are determined by the
electron configuration
Ions
• Atoms that have a charge
• Have lost or gained an electron
Electron Shielding
• Electrons on the inner levels shield the
valence electrons from the attractive force of
the positive nucleus
Ionization Energy
• The energy required to remove an electron
from an atom
• Decreases as you move down a group
(the valence electrons are farther from nucleus)
• Increases as you move left to right across
(more protons for the same # of energy levels)
More on Ionization Energies
• First ionization energy – The energy required to remove the
first electron
• Second ionization energy - . . .
• The more electrons removed the more energy it takes
MC Test Question: Which Ionization energy is
the Largest?
Electronegativity
• How much an atom in a compound attracts
electrons
• More protons = greater positive charge
Atomic Radius
• Bond Radius – half the distance between the nuclei of two
bonded atoms
• Increases as you move down a group (more energy levels)
• Decrease as you move across
(more protons for the same # of energy levels)
Ionic Size
• Increases moving down a column
• Decreases moving across a row
Electron Affinity
• The change in energy when a neutral
atom gains an electron
• Zero for the Noble gases
Melting and Boiling Points
WHERE DID THE
ELEMENTS COME
FROM?
Section 4-4
The “Big Bang”
• The beginning of the universe, 13.7 billion ybp
• Only energy existed, no matter
• Hydrogen and some Helium atoms form
Nuclear Fusion in Stars (including Sun)
• Intense pressure
cause nuclei to fuse
• Creates other
elements
• Releases energy
(light and heat)
Nuclear
Fusion
• All
elements
up to 26
(Iron)
form in
stars
Elements heavier then Iron
• Only a supernova is powerful enough to
fuse elements heaver then iron
Transmutation
Synthetic Elements
Superheavy Elements