271975
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The periodic table CH.4
- The elements
- Greek philosophers;
four elements earth, air,
water, fire.
- Robert Boyle described an
element as a substance that
cannot be broken down into
simpler substances by chemical
means
- elements combine together in a
chemical reaction to form a compound.
- Humphry Davy discovered
many elements by passing
electricity through their
compounds.
- The discovery of the
fact that that an electric
current could be used to
obtain elements from
their compounds was a
turning point in the
history of the discovery
of the elements.
- The discovery of the
fact that that an electric
current could be used to
obtain elements from
their compounds was a
turning point in the
history of the discovery
of the elements.
- Henry
Mosley used
x-rays to
discover a
method of
determining
the number
of protons in
the nucleus
of an atom
- No 2 elements have
the same number of
protons.
- No 2 elements have
the same number of
protons.
- Greek philosophers;
four elements earth, air,
water, fire.
- Johann Dobereiner.
- Dobereiner looked at the
properties of various elements in
an attempt to find some order
among them.
- The modern name for atomic
weight is a 'relative atomic mass'.
- A triad is a group
of 3 elements with
similar chemical
properties in which
the atomic weight
of the middle
element is
approximately
equal to the
average of the
other 2.
- Dobereiner looked at the
properties of various elements in
an attempt to find some order
among them.
- Newlands Octaves.
- Arranged
the
known
elements
in order
of their
atomic
weight.
- Newlands law of octaves are
groups of elements arranged in
order of increasing atomic
weight, in which the first and
eighth element of each group
have similar properties.
- Newlands tried to force all the
known elements to fit into his table.
newlands law of octaves worked for
only about the first 16 elements. the
elements were forced into the
wrong group.
- Arranged
the
known
elements
in order
of their
atomic
weight.
- Dmitri Mendeleev
- He found that if the
elements were arranged in
order of increasing atomic
weight, then every eighth
element had similar physical
and chemical properties.
- Mendeleevs periodic law =
whenelements are arranged in
order of increasing atomic weight,
the properties of the elements
vary periodically.
- Mendeleev left gaps in his
table to make the elements fit
into the proper column.
- gaps
represented
elements
that had not
yet been
discovered.
- He even
predicted the
properties that
the
undiscovered
element should
have.
- gaps
represented
elements
that had not
yet been
discovered.
- He found that if the
elements were arranged in
order of increasing atomic
weight, then every eighth
element had similar physical
and chemical properties.
- Henry Moseley.
- He discovered a method of determining
the number of protons in the nucleus of
an atom (atomic number)
- The
atomic
number
of an
atom is
the
number
of
protons
in the
nucleus
of that
atom.
- the modern periodic table is an arrangement of
elements in order of increasing atomic number.
- When
elements are
arranged in
order of
increasing
atomic
number, the
properties of
the elements
vary
periodically.
- He discovered a method of determining
the number of protons in the nucleus of
an atom (atomic number)
- The modern periodic
table VS mandeleevs
periodic table.
- MoPT=arranged in order of
increasing atomic number
- MePt= Arranged in order of
increasing atomic weight.
- MePt= Arranged in order of
increasing atomic weight.
- MoPT= more
elements,
noble gases,
no gaps.
- MoPT=
transition
elements
are listed
in a
separate
- MoPT=arranged in order of
increasing atomic number
- Atomic
numbers
and mass
numbers.
- The mass
number of
an element
is the sum
of the
number of
protons
and
neutrons in
the
nucleus of
an atom.
- eg. sodium has 11
protons and 12
neutrons therefore
the mass number is
23 (11+12=23)
- eg. sodium has 11
protons and 12
neutrons therefore
the mass number is
23 (11+12=23)
- masses of atoms are so
small they are not normally
measured in grams. a
special unit is used called
the atomic mass unit.
- 1a.m.u. = 1.66X 10^-24 gram
- 1a.m.u. = 1.66X 10^-24 gram
- Z = atomic number.
- A=mass number
- A-Z= number of neutrons.
- A-Z= number of neutrons.
- A=mass number
- The mass
number of
an element
is the sum
of the
number of
protons
and
neutrons in
the
nucleus of
an atom.
- Relative atomic mass isotopes.
mass spectrometer.
- Mass
spectrometer
used to
measure the
masses of
atoms.
- 1) Sample inlet. liquids turn
to gases in the instrument.
called VAPORISATION.
- 2) Ionisation chamber. turns
atoms or molecules into ions.
done using an electron gun.
positive ions are produced.
- 3) Accelerator. accelerates
positive ions to high speeds.
then passed into the analyser.
- 4) separation unit (magnetic
field). positive ions are made
move in curved paths using a
magnetic field produced by a
powerful electromagnet. lighter
particles - easier to deflect.
heavier particles- difficult to
deflect. lighter ions are pushed
further off course than the
heavier ones. therefore the ions
are separated according to their
masses.
- 5) detector. the detector
responds to the number of
ions hitting it. by changing
the strength of the magnetic
field. the operator brings ions
of different masses to focus
on the detector. the signal is
then amplified and sent to the
recorder.
- mass spectometer is
used to identify the
presence of isotopes,
measure the relative
atomic and molecular
masses, and identify
unknown compounds.
- 1) Sample inlet. liquids turn
to gases in the instrument.
called VAPORISATION.
- isotopes are atoms of the
same element that have
different mass numbers due
to the different number of
neutrons in the nucleus.
- average mass of
an atom is
measured relative
to the mass of the
carbon-12 isotope
for this reason it is
called its relative
atomic mass.
- Mass
spectrometer
used to
measure the
masses of
atoms.
- electronic configurations.
- aufbau pricipal states that when building
up the electronic configuration of an atom
in its ground state, the electrons occupy
the lowest available energy level.
- n=1=1s^2,
n=2=2s^2 2p^6,
n=3=3s^2 3p^6
3d^10, n=4= 4s^2
4p^6 4d^10 4f
- Hunds rule of
maximum multiplicity
states that when two or
more orbitals of equal
energy are available,
the electrons occupy
them singly before
filling them in pairs.
- The Pauli
exclusion principal
states that no
more than two
electrons may
occupy an orbital
and they must
have opposite
spin.
- aufbau pricipal states that when building
up the electronic configuration of an atom
in its ground state, the electrons occupy
the lowest available energy level.
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