Task 3 Andrew Borthwick- Clarke
Q1)
Element
Number of Protons
Li
Na
K
Rb
Cs
3
11
19
37
55
First ionisation Energy
(kJmol)
520
496
419
403
376
Q2)
First ionisation Energy
600
500
400
300
First ionisation Energy
200
100
0
0
10
20
30
40
50
60
X-Axis= Number of Protons (Li, Na,K,Rb,Cs)
Y-Axis= First ionisation energy (kJmol)
3)
The first ionisation energy decreases as we move from top to bottom in the
above information. This is because the distance between the nucleus and the
further most electrons increases. This increase in distance between the
nucleus and electrons therefore means that the level of attraction decreases.
Shielding also plays a role in this decrease of ionisation energy. Shielding
electrons are the electrons in the energy levels between the nucleus and the
valence electrons. They are called "shielding" electrons as they "shield" the
valence electrons from the force of attraction exerted by the positive charge in
the nucleus.
As we can see from the above graph, Lithium has a larger first ionisation
energy compared to that of Potassium and Caesium.
4)
Element
Li
Na
K
Rb
Cs
Atomic Radius (Pm) Pico metres
145
186
220
248
260
Atomic Radius
300
250
200
150
Atomic radius
100
50
0
0
10
20
30
40
50
60
X-Axis= Number of protons, (Li, Na,K,Rb,Cs)
Y-Axis= Atomic Radius (Pm)
5) As we go down the Group, the atomic radius increases. This is because
there is more electrons, the more electrons the more number of shells hence
a larger atomic radius.
6) Looking at the above information, we can tell that the reactivity in the group
increases as we move from the top to the bottom of the groups. The reactivity
increases as the atomic radius increases; this increase in atomic radius
means there is more distance between the nucleus and the outer electrons
meaning that the element is able to loose its outer electrons easier than that
of elements with small atomic radiuses. For example Lithium has an atomic
radius of 145 pm, it has one valence electron (-1, loose an electron) this is
hard as there is a larger attraction force between the nucleus and the
electrons.
Caesium has an atomic radius of 260 pm, it has one valence electron which it
wants to loose. This electron can be lost considerably easier as it has many
shells (less attraction), making caesium far more reactive than lithium.
2Li+2H20 -> 2LiOH +2H2
2Cs+2H20 -> 2CsOH +2H2
Observation Lithium: Lithium has a low density making it float on water, there
is a little fizzing, once the fizzing finishes it returns into a colourless solution
with gas being given off, the reaction gives off a little amount of heat slowly,
but it does not melt as hit has a very high melting point.
Observations Caesium: Caesium explodes on contact with water, shattering
the container it is in. during the reaction hydrogen gas is given off.
From these observations we can tell that caesium is far more reactive.
7) Group two will show a similar pattern to that of group one. The first
ionisation energy decreases as we move down the group. This is because the
distance between the nucleus and the further most electrons increases. This
increase in distance between the nucleus and electrons therefore means that
the level of attraction decreases. Shielding also plays a role in this decrease
of ionisation energy. Shielding electrons are the electrons in the energy levels
between the nucleus and the valence electrons. They are called "shielding"
electrons as they "shield" the valence electrons from the force of attraction
exerted by the positive charge in the nucleus.
Below is a table of first ionisation energies of group 2.
Element symbol
Number of Protons
First ionisation energy
(jKmol)
Be
4
900
Mg
12
738
Ca
20
590
Sr
38
550
Ba
56
503
Comparing the above table to that of question 3, we are able to see that the
first ionisation energy is decreasing.
The below website supports the above answer.
http://www.creative-chemistry.org.uk/alevel/module1/trends2.htm
8)
Element
Number of Protons
Li
Be
B
C
N
O
F
Ne
3
4
5
6
7
8
9
10
9)
First Ionisation Energy
(Jkmol)
520
900
801
1806
1402
1314
1681
2081
First ionisattion Energy
2500
2000
1500
First ionisattion Energy
1000
500
0
0
2
4
6
8
10
12
X-Axis= Number of protons (Li, Be, B,C,N,O,F,Ne)
Y-Axis= First ionisation energy
10) Looking at the above graph, we can see that there is an increase and
decrease in the first ionisation energy. Overall there is a general increase with
the first ionisation energies of period two. Moving from left to right, there is an
increase in the number of protons; this therefore means there is an increase
in the nuclear charge in the elements. The attraction forces between the
nucleus and the outer electron is also increasing, there is lower increase in
shielding s we move left to right as each of the electrons enter the same
energy levels. Therefore meaning a higher first ionisation energy is required.
11)
Element
Number of protons
Li
Be
B
C
N
O
F
Ne
3
4
5
6
7
8
9
10
12)
Electronegativity
(Pauling)
0.98
1.57
2.04
2.55
3.04
3.44
3.98
0
Electronegativity
4.5
4
3.5
3
2.5
electronegativity
2
1.5
1
0.5
0
0
2
4
6
8
10
12
X-Axis= Number of protons (Li, Be, B,C,N,O,F,Ne)
Y-Axis= Electronegativity (Pauling)
13) As we move from left to right across the periodic table (period 2), we can
see that the electronegativity increases, other than the odd exception of Neon.
Electronegativity is the relative ability of an atom to attract the bonding
electron pair in a covalent bond. From the move graph we can tell that the
nuclear charge increase, the atomic radius decreases; there is an increase in
number of electrons, but a low increase in shielding. This low increase in
shielding is responsible for the increase in electronegativity. This is because
there is a higher attraction between the nucleus and electrons, therefore
making it harder to bond with other elements. Neon has the exception as it
has full outer shells, therefore meaning it will not bond with other elements
meaning no electronegativity.
14) The reactivity moving across the period decreases. This is due to the
increase in attraction between the nucleus and the outer electrons (shielding).
This increase in attraction makes it harder for an element to gain or loose
electrons to bond with other elements. As it is harder for it to bond with other
elements we are therefore able to say that it is less reactive than that of one
of the elements on the left hand side.
15) Neon is considered to be very non-reactive as all the electron shells within
the atom are full. This therefore means that it neither looses nor gains
electrons, hence unable to form covalent bonds. It also has a electronegativity
of zero, this is due to it not needing to ionise/ loose or gain electrons.