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Chapter 4
The Periodic Table
Organizing the Elements
Mendeleev – Constructed the first
Periodic Table in 1869 The elements were
arranged according to their chemical
properties
 Vertical columns were in order of
increasing atomic mass
 The columns were arranged so that
elements with the most similar properties
were side by side
 Dmitri
 Mendeleev
even left blank spaces for
elements that he believed existed, but
were not yet discovered, one example
was…
 Ekasilicon… now element 32 Germanium.
Moseley – in 1913 Moseley, a
British physicist determined an atomic
number* for each known element and
arranged the Periodic Table by order of
atomic number.
 This is the way the Periodic Table is
arranged today.
 Periodic Law: When elements are
arranged in order of increasing atomic
number there is a periodic repetition of
Physical and Chemical properties.
 Henry
Metals Nonmetals and Metalloids
 Over
80% of the elements are Metal
 Metals are...
 Good Conductors of heat and
electricity
 Metallic luster or sheen, its ability to
reflect light.
 Malleable: Ability to be hammered
into sheets or foil.
 Ductile: Ability to be drawn into
wire.
 Solid @ room temp (except Hg)
 Nonmetals
are located in the upper right
corner of the periodic table, to the right of
the stair shaped line.
 Nonmetals have a great variation in
physical properties…gases, solids, one
liquid Br.
 Nonmetals are poor conductors, their
solids are brittle.
 Metalloids
are located on the stair shaped
line, outlined on our chart in green.
 Metalloids have properties of both metals
and non metals. In general they…




Have metallic luster
Conduct electricity, but not as well as a metal,
(semiconductor)
Are brittle, they will shatter if hit with a
hammer.
They are used extensively in the electronics
industry for computer chips and circuits.
– the horizontal rows of the
Periodic Table.
 Groups – the vertical columns of the
Periodic Table.
 Periods
Classifying the Elements
Noble gases – elements in which the
outermost s and p sublevels are filled. Group
18 on the chart.
Representative elements – elements whose
outermost s and p sublevels are only partially
filled. Groups 1,2 and 13-18 on the chart (tall)
1.
2.
1.
2.
3.
4.
Group 1 = alkali metals
Group 2 = alkaline earth metals
Group 17 = halogens
Group 18 = noble gases
cont.
3. Transition metals – elements whose
outermost s sublevel and the nearby d
sublevel contain electrons (Groups 3-12)
4. Inner transition metals – elements whose
outermost s sublevel and nearby f sublevel
contain electrons… the two rows below
the table
6.3 Periodic Trends
 Atomic
Radius: Is one half the distance
between the nuclei of two atoms of the
same element when the atoms are joined.
 “In general, atomic size increases from top
to bottom within a group and decreases
from left to right across a period…”
 Largest in the lower left corner.
cont. Ions

An Ion is an atom or group of atoms that have a
positive or negative charge.
 Positive and negative ions form when electrons
are transferred between atoms.
 Cations are positive ions… (generally metals)
formed when atoms lose electrons to obtain the
electron configuration of a noble gas.
 Anions are negative ions… (generally
nonmetals) formed when atoms gain electrons
to obtain a noble gas electron configuration.
Ionization energy
energy – the energy required to
overcome the attraction of the nuclear
charge and remove an electron from a
gaseous atom.
 Ionization


The ionization energy decreases as you move
down a group of the periodic table
The ionization energy increases as you move
across a period of the periodic table
Ionic Size
 Positive
ions are smaller than the atoms
they are formed from
 Negative ions are larger than the atoms
they are formed from


Ionic size tends to increase as you move
down a group in the periodic table
Ionic size tends to decrease as you move
across a period in the periodic table
Electronegativity
– the tendency for the
atoms of the elements to attract electrons
when they are chemically combined with
another element
 Electronegativity


Electronegativity tends to decrease as you
move down a group in the periodic table
Electronegativity tends to increase as you
move across a period in the periodic table