Transcript 6.1 Organizing the Periodic Table

Warm-up 11/21
Watch the video and describe how
one scientists changed aspects of the
previous theory to make a new one.
Organizing the Periodic Table
Chemists use the
properties of elements to
sort them into groups
Warm-up 11/25
• Use the periodic table to find the following
information on Fluorine.
–
–
–
–
Group #
Period
# of Valence Electrons
# of Energy Levels (shells)occupied by the
electrons in Fluorine
Mendeleev’s Periodic
Table
Eka aluminum
• 1869- Russian chemist & (gallium) predicted it
would be a soft metal
teacher published the first table
with a low melting
of elements to be widely point and a density of
accepted
5.9 g/cm3 close
match=useful table!
• Arranged the elements into rows
in order of increasing mass so
that elements with similar
properties were in the same
column
• Left empty spaces where
undiscovered elements would fit
12/1 Warm-up
• Describe 3 pieces of information that
you can get from the periodic table
about an element.
12/2 Warm-up
Determine which of these images is a
metal, nonmetal and metalloid and
write the clues you used to decide.
The Modern Periodic Table
• An arrangement of elements based on a set of properties that repeat
from row to row
• Elements are arranged according to atomic number
• 7 rows or periods- each corresponds to a principle energy level- the
# of elements per period varies because the # of available orbitals
increases from energy level to energy level
• Elements within a column or group have similar properties
• Properties w/in a period change as you move across the row, the
pattern repeats as you move from one period to the next
Periodic Law
• When elements are arranged in order of
increasing atomic number, there is a periodic
repetition of their physical and chemical
properties
Atomic radii
decreases
Electronegativity
decreases
Sodium
Potassium
Metals
• 80% of elements
• Good conductors of
heat and electricity
• High luster- reflect light
• Solids at room
temperature
• Ductile
Nonmetals
• Show greater variation in
physical properties
• Most are gases at room
temp.
• Properties opposite metals
– Poor conductors
– Brittle
Metalloids
• Show properties similar to metals and
nonmetals depending on conditions
Use the atomic # to find the # or
protons or electrons (in a neutral
atom)
Mass #-Atomic
#=neutrons
Round atomic mass
to the nearest
whole # to get
mass #
Representative Groups
• Valence electron- electron
that is in the highest occupied
energy level of an atom
• Valence electrons play a key
role in chemical reactions
• Properties vary across a
period because the # of
valence electrons increases
from left to right
• Elements in a group have
similar properties because
they have the same # of
valence electrons
Valence Electrons
• When the highest
occupied energy level of
an atom is filled with
electrons, the atom is
stable and not likely to
react.
• Electron dot diagram- a
model of an atom in
which each dot represents
a valence electron
Ionic Bonds
• Elements that do not have
complete sets of valence
electrons tend to react.
• Some elements achieve stable
electron configurations
through the transfer of
electrons between atoms.
• When an atom gains or
loses an electrons the # of
protons does not equal
the # of electrons this
forms an ion
• Ion- charged atom
• Formation of an ion
requires energy because
an electron must be
removed
Anions are named by using
part of the element name
and the suffix -ide
To become an ion an
elements electron must
escape the energy levels by
gaining a required about of
energy called the ionization
energy.
Formation of Ionic Bond
• An ionic bond is an
attraction between a
cation (metal) and an
anion (nonmetal)
• A ionic compound is a
compound that
contains ionic bonds
and the net charge
must be zero
Crystal Lattices
Ionic Compounds
have high melting
points, are poor
conductors as solids
(good when melted or
in solution), and
shatter when struck
with a hammer.
Covalent Bonds
• Nonmetals will
sometimes share electrons
to achieve a full set of
valence electrons
• A chemical bond in which
two atoms share electrons
is a covalent bond
• The attraction between
the shared electrons and
the protons in each
nucleus hold the atoms
together.
Electron
dot formula
Structural
Formula
Covalent Bonds
• Some atoms share
more than one pair of
electrons to reach a
full outer shell of
electrons.
• Two pairs of
electrons- double
bond
• Three pairs of
electrons- triple bond
Polar Covalent Bonds
• In a covalent compound
with more than one type
of atom the electrons may
not be shared equally
• In general, elements on
the right of the periodic
table and at the top of
groups have a greater
attraction for electrons
(electronegativity)
A covalent bond in which the
electrons are aren’t shared
equally is a polar covalent bond
Polar and Nonpolar Molecules
• In a polar covalent bond the
atom with the greater
attraction for electrons has a
partial negative charge and
the other atom has a partial
positive charge.
• An atom can have a polar
bond and not be a polar
molecule.
• The type of atoms and its
shape determine whether a
molecule is polar or not.
Which of
these are
polar??
Attraction Between Molecules
•
There are forces of attraction
between molecules they are
not strong as ionic or
covalent bonds but they are
strong enough to hold
molecules together in a solid
or a liquid
• Attractions between
polar molecules are
stronger than
attractions between
non-polar molecules
Metallic
Bonds
• The attraction
between the metal
cation and the shared
electrons around it
• In a metal the valence
electrons are free to
move among the
atoms- this accounts
for many of the
properties of metals
Chemical Reactions
• In a chemical reaction
one or more reactants
react to form one or
more products
• Chemical Equations
are used to represent
the process of a
chemical reaction.
• Reactants  Product
• Mass is neither
created or destroyed
during a chemical
reaction so the
number of atoms on
either side of the
equation must be
equal.
Balancing Equations
• In order to show that mass is
conserved during a chemical
reaction the equation must be
balanced.
• Equations are balanced by
changing the coefficient's (the
numbers in front of the formulas)
• NEVER CHANGE THE
SUBSCRIPTS- THAT CHANGES
THE IDENTITY OF THE
REACTANT OR PRODUCT
• Synthesis- two or more substances react to
form a single substance
• A + B  AB
• Balance this one
– Na + Cl2  NaCl
Decomposition Reactions
• A reaction in which a compound breaks
down into two or more simpler substances.
• AB  A + B
• Balance this one- H2O  H2 + O2
• Reaction in which one element takes the
place of another.
• A + BC  B + AC
• Balance this oneCu + AgNO3  Ag + Cu (NO3)2
• Two different
compounds exchange
positive ions and form
two new compounds
• AB + CD  AD + CB
• Try ThesePB(NO3)2 + KI  PBI2 + KNO3
CaCO3 + HCL  CaCL2 + H2CO3
A substance reacts
rapidly with oxygen
often producing heat and
light
• Balance these
CH4 + O  CO2 + H20
H2 + O2  H2O