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Transcript of In a video store, the latest movies are usually placed on the shelves in alphabetical order. Older...
In a video store, the latest movies are usually placed on the shelves in alphabetical
order. Older movies are grouped into categories such
as Action or Comedy. The manager has to choose a set of categories and then place each movie in the most appropriate
location.
Scientists faced a similar challenge when they looked for a logical way to organize
the elements.
Mendeleev arranged the elements into rows in order of increasing
mass (not atomic #) so that elements with
similar properties were in the same column.
There was a hole in this table… a missing element that had not been discovered at the time. Mendeleev predicted the properties of a missing element in his table. He said that eka-aluminum would be a soft metal with a low melting point and a density of 5.9 g/cm3.
Gallium is a soft metal with a melting point of 29.7°C and a density of
5.91 g/cm3.
The close match between Mendeleev's predictions and the actual properties of
new elements showed how useful his periodic
table could be.
In the modern periodic table, elements are
arranged by increasing atomic number (number of
protons).
periodic lawthe pattern of repeating properties
displayed by elements in the periodic table
Groups are verticaland have similar properties
Group 1 = H through Fr
Periods are horizontalPeriod 2 = Li through Ne
Elements are classified as metals, nonmetals,
and metalloids
Metals are elements that are good conductors of
electric current and heat.
Most metals are malleable, they do not shatter when hit. Many
metals are ductile; that is, they can be drawn into
thin wires.
Nonmetals are elements that are poor conductors
of heat and electric current. All the gases in
the periodic table are nonmetals. The nonmetals
that are solids at room temperature tend to be
brittle. If they are hit with a hammer, they shatter or
crumble.
Metalloids are elements with properties that fall
between those of metals and nonmetals. For
example, metals are good conductors of electric
current and nonmetals are poor conductors of electric
current.
The elements in Group 1 are called alkali metals. These metals have s1 electrons and are extremely reactive(Group 2-alkaline earth metals, Group17-Halogens, p.162)
Group18 noble gases. Helium s2
all others are stables2p6
s, p, d, f blocks
Electronegativity – how much the nucleus wants the electron
Atomic radii decreases as electronegativity increases.
Ions- have lost or gained electrons
• Would something with a high electronegativity want to lose or gain electrons?
Sketch a table, and leave some space
Periodic Trends
First ionization energy – energy needed to remove 1 electron
Which would take more energy to remove an electron from?
Fluorine or Oxygen
Electrons have a negative charge
• How does the charge of an atom change if the atom gains an electron?
• How does the charge of an atom change if the atom loses an electron?
Atom vs Common Ion Radii p 178
• Ions with positive charges are smaller than atoms (lost electrons)
• Ions with negative charges are larger than atoms (gained electrons)