AS-Level Chemistry :Paper 1 2024
latest update graded a+
Arranged in periods (rows) and groups (columns) by atomic (proton)
number - CORRECT ANSWER-How is the periodic table arranged
Have the same number of electrons shells, even if they are not all
parts of the s or p sub-shells - CORRECT ...
,Arranged in periods (rows) and groups (columns) by atomic (proton)
number - CORRECT ANSWER-How is the periodic table arranged
Have the same number of electrons shells, even if they are not all
parts of the s or p sub-shells - CORRECT ANSWER-All elements
within a period ...
Have the same number of electrons in their outer shell, meaning
that they all have similar properties - CORRECT ANSWER-All
elements within a group ...
Periodicity - CORRECT ANSWER-The trends in the physical and
chemical properties of elements as you go across the periodic
table.
Atomic radius across period 3 - CORRECT ANSWER-Atomic radius
across period 3 goes as follows:
1) As the number of protons increases the further down a period you
go, the positive charge of the nucleus increases
2) And though the amount of electrons increases across a period,
they are added to the outer energy level - So their isn't any extra
shielding
3) This means that the electrons are pulled closer to the nucleus,
causing the atomic radius to decrease
,4) Therefore, that overall the atomic radius of an atom decreases
across period 3 with the largest radius being the first element, Na,
and the smallest being the last element, Ar
Melting points across a period 3 - CORRECT ANSWER-The melting
point across period 3 goes as follows:
1) At the start with sodium, magnesium and aluminium their melting
points increase. This is because they are metals and have strong
electrostatic forces to overcome - The bonds get stronger by the
time you reach Al due to having and more positively charged
nucleus, increased number of delocalised electrons and a
decreasing radius
2) From Al to Silicon, the melting point increases further as Si is a
macromolecular substance which has very strong covalent bonds
that take a lot of energy to break
3) However, the melting point then drops due to phosphorus, sulfur,
chlorine and argon all being molecular substances. The issue with
being that kind of substance is that to break the bonds apart all you
need to do is to overcome the weak Van der Waals forces - A very
easy task
4) The difference in melting points between P, S, Cl and Ar is that
some molecules are bigger than others which leads to slightly
greater Van der Waals forces
First ionisation energy across period 3 - CORRECT ANSWER-First
ionisation energy across period 3 goes as follows:
, 1) As you mover across the period, the general trend is for the
ionisation energy to increase - This is due to an increase in number
of protons within an atom as you go across the period which leads
to a stronger nuclear attraction
2) The electrons do not counter this increase in protons due to the
electrons remaining in roughly the same energy level which means
their is little shielding affect or extra distance to lessen the
attraction from the nucleus - Though there is a dip between
elements in Mg and Al, P and S
3) The issue between Mg and Al is that Al has a 3p outer orbital
rather than the 3s on Mg. Because of this the outer most electron in
Al is further away from the nucleus and has an extra layer of
shielding in the form of a 3s
4) As for the drop from P to S, this is because, though the ionised
electron come out of the same sub-shell for both P and S. However,
in P case the electron is being removed from a single occupied shell
whereas is is being removed from an orbital containing two in S. The
repulsion between the two electrons means that the electrons are
easier to remove from shared orbital
Increases as you go down the group due to extra electron shells as
you go down the group - CORRECT ANSWER-Atomic radius across
group 2
First Ionisation Energy down Group 2 Alkali Metals - CORRECT
ANSWER-First ionisation energy down Group 2 Alkali Metals goes as
follows:
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