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OCR AS Level Chemistry Module 3 Periodic Table and Energy
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This is the second theory module from the OCR AS Level chemistry course.
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PERIODIC TABLEAND ENERGY
The Periodic Table
Groups, Periods and Blocks
The periodic table a l l te
hle
e m e n ts by proton from lowest to
arranges
number
highest.
·
Periods
↳ A in the
r ow
periodic table.
↳All elements
t h e i r valence electron in the
with same shell
go
in the same
period.
·
Groups
↳ A in the
c olumn periodic table.
↳Elements in the
group have
same their electrons in similar orbitals
↳ Often have similar properties.
↳Have the same amount of electrons in their o u te r shell.
·
Blocks
↳ The two most left columns make block.
the
up
↳ All the elements in this block have their valence electrons in sorbitals.
Helium
↳
is too in this block.
↳ The the p block.
six
rightmostcolumns make up
↳ All the elements in this block have
partially filled
a
p sub-shell.
↳ d Block lies betweenthe sand
p block.
↳Elements in a block a sub-shell.
have
partially filled
a
↳ The f block is detached
along t h e bottom of the
periodic table.
↳ Elements f block have filled of sub-shell.
in the a
partially
Ionisation Energy
Ionisation energy is the
energy required
to re m ove one mole of
e lectrons
from mole of ions.
one
gaseous atoms or
Xigter) standtesterent
First Ionisation
Energy: Xig -> Xg+e-
Second Ionisation
Energy: Xyl-Xg+e= &
Third Ionisation Energy. Xig
->
,Factors Affecting
Ionisation Energy
·
Distance from t h e nucleus
↳Electrostatic attraction decreases the further electrons a re from nucleus.
↳ Less
energy is needed to re m ove electrons which a re further
away.
↳Therefore as distance increases, ionisation decreases.
energy
Nuclear
charge
·
↳ The the number of
greater protons in the nucleus, the
greater the attraction
of the electrons the
to nucleus.
↳ More is needed remove the electron.
energy
to
↳
Therefore, ionisation
energy is
greater.
·
Shielding
↳The the number of
e lec trons between the
greater nucleus and outer
the electrons,
the lower the effectiveness of
nuclear
charge.
↳Positive electrons
charge that
gets elec trons is
to reduced bythe in between.
↳The the number of ionisation
greater electrons, the lower the
energy.
Ionisation Energy Graph of Sodium
·
The graph shows the trend i n successive
ionisation of sodium. This evidence
energies
for the structure of an atom.
·
Ionisation energy increases with proximityto
the nucleus.
↳
The ionisation
1
n= shell will have a
higher
than the 2 shell.
energy n
=
↳ The 2
n= shell will have a
higher ionisation
energy than the n 3 shell
=
Trends in Ionisation
·
Down a
group
First
↳
ionisation energies decrease.
↳
This is because the atomic radius increases.
↳
Electron is further away from nucleus so
experiences less attraction.
↳ There a re also m o re electrons between the nucleus and the outer electrons.
↳ Outer electrons experience m o re
shielding therefore do not
getthe full attraction.
Across
·
a
period
↳First
ionisation
energy increases.
↳ Atomic radius decreases. Proton number increases electrons a re attracted
across a
period so m o re
to the nucleus.
↳ The electron is closer t h e nucleus attraction.
to so
experiences greater
Nuclear
↳
charge increases across a
period.
, Metallic Bonding and Structure
Metals bond in a different way
to non-metals.
·
Seaoffree electrons
↳ In a metal, the valence electrons delocolise, an d can m ove around the
entire metal.
↳ Metalic sec off ree electrons
bonding is viewed as a
surrounding positive
you cores.
↳The
positive ion core s a re attracted to the free electrons.
·
Electrical conductivity
↳Metals a re
good
electrical conductors because the free electrons can
m ove a n d cur rent.
carry
↳
They a re called
charge car riers.
Melting
·
point
↳Related to the
groupof
the metocl.
↳
Ag roup
2 metal will donate two electrons to the sea of electrons.
↳Positive ion
charge.
h e re 2+
c o re s
carry a
↳
The 2+ ion
stronger attraction to the free electrons.
has a
Melting point is higher.
↳
↳
E.g. Sodium melts a t 98°, Magnesium melts a t 650°C.
Structure ofSolid State Metorls
Metals in a solid state can be defined
by atoms
arranged in rows and held
together through
the principles of metallic
bonding.
·
Metolic lattices
↳ All metals, when solid, their
display atoms in a
giant metallic lattice.
↳Atoms a re
arranged in
regular rows, held in place through electrostatic attraction
between the positive metal ions and their delocolised electrons.
↳ Rows s
able t ol i d e ove r each to bend and be
a re
other, giving metals the ability
beaten into shape (malleable).
Melting and
boiling points
·
↳Metals have a
high level ofa ttrac tion between the metal ions and the electrons.
↳ This they
means, require a lot of
energy
to be
separated and therefore
high melting
and
boiling points.
↳Metals with delocolised electrons tend
m o re to have
higher melting and
boiling points.
·
Electrical conductivity
↳Metals a re
good
electrical conductors because the free electrons can
m ove a n d cur rent.
carry
↳
They a re called
charge car riers.
Strength ofattraction
·
↳ There is the
a
strong attraction between positive metallions and
negative electrons.
↳The easily.
strength of these attractions means metals do not dissolve
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