Wednesday, 30 December 2015
Sunday, 27 December 2015
Reaction of Group-2 Metals with Chlorine Gas :
Reaction of Group-2 Metals with Cl2 :
All Gr-2 metals except Be
react with chlorine to give ionic chlorides whereas Be reacts with chlorine to
give covalent chloride.
The equations for the reactions:
All metal chlorides above are white ionic solid.
Beryllium reacts with chlorine to form polymeric
BeCl2.
Here are some video tutorials about some other problems. Click the following link to visit:
Saturday, 26 December 2015
Reaction of Group 2 metals with oxygen:
Reaction of Group-2 metals with oxygen :
Hi
fellows!! This is Chemaddicts again to
the solution. Today, we will discuss about the reaction of Gr-2 metals with
oxygen.
So, let’s get started!!
Before going to
the discussion of the reaction of Gr-2 metals with oxygen, we need to clear the
confusion between the concept of burning metal
and metal ions .
Most of the
students mix up the concept of burning metals and metal ions.
This is because
most metals and metal ions in Gr-2 have same flame colour. There is a difference
and we will see today:
Today, we will discuss
the reaction of metals with oxygen gas:
All Gr-2 metals except Barium react with oxygen to give
metal oxides whereas Barium reacts with oxygen to give Barium
peroxide ( BaO2 ).
Equations for
the reactions:
Here Mg burns with bright white flames.
Here, in this
case , we are burning Mg not Mg ion .
This is the difference here. Mg2+ ion have no flame colour. Don’t write
the flame colour of Mg2+ ion
as Mg metal.
Other Group-2 metals
below Mg give the same colour as the metal cations. So, don’t get confused.
Here Ca burns with brick red flames like Ca2+ ions.
Here Calcium metal will give the same colour as the Ca2+ ion.
Here Strontium metal will give the same colour as the Sr2+ ion.
(Here Ba burns with apple green flames like Ba2+
ions. )
Here Barium
metal will give the same colour as the Ba2+ ion.
If you wanna have some other video tutorials, you will find them here:
What Are The Group-2 Elements ?
The Periodic Table (
Group – 2) :
Hi fellows!!
Today we are going to analyse Group-2 Metals in this discussion.
At first, let us
look at elements of Group-2.
Trend in ionisation energy down the Gr-2 :-
Down the Group-2
:-
Size/
Radius of cations increases.
Nucleus
become more shielded.
Nuclear
charge increases but it is not the dominating factor here.
Therefore
ionisation energy decreases.
If you want to watch video tutorials, please click the following link :
Thanks for watching !!! Bye !! Bye !!! See you in next post!!!
Thursday, 24 December 2015
The ionic and covalent character of an ionic compound:
Hi fellows ,
this is Chemaddicts to the solution!!!!
Today we are going
to discuss about the Covalent and ionic
character.
So let’s get
started !!
We will come to know
about the following concepts :
1) Covalent
character
2) Ionic
character
3) The
relationship between ionic and covalent character.
1) Covalent character :
What is a
covalent character ?
A covalent
character is the covalency in ionic compounds which is due to the
High Polarising power of Cations and High
Polarisability of anions.
Diagram :
Then gradually,
Finally the oxide ion is being distorted by Magnesium ion... |
High Polarising power of Cations :
- It is the ability of a cation to distort the electron cloud of the anion in an ionic compound.
- Higher polarising power of cations means that ionic compound gains more covalent character.
Polarising power of cation depends on :
1) Size of Cations .
2) Charge of Cations . ( Not the Nuclear charge )
Diagram :
Here charge of the ions are involved here , not the nuclear charge. |
1) Size of Cations :
- Decreasing size of cations results in greater polarising power. From here, we can deduce that :
Here charge of cations are same (constant).
Therefore, small cations can distort the electron cloud
of anions more effectively.
2) Charge of Cations:
- Increasing Charge on Cations ( Not the nuclear charge ) results in increasing the Polarising power of Cations.
- Greater Charge on Cations means it can have more attraction with the electron cloud of anions.
A new
relationship can be obtained between Polarising power and the following
factors :
1) Size of
Cations
2) Charge of Cations
Now we are combining
the equations that we have derived before,
Where,
Charge Density:
It is simply a ratio
of charge and size.
Polarising power cations down the Group:
Polarising power of cations decreases
down the group.
Let’s see how,
LiCl * Charge
on the cations remain same.
NaCl * Size
of Cations increases .
KCl * Charge density of cations decreases.
RbCl * So, the anions are distorted less.
CsCl *
Covalent Character decreases
* Ionic
Character increases
Down the Group 2 ionic compounds ,
BeO * Charge
on the cations remain same.
MgO * Size of Cations increases .
CaO *
Charge density of cations decreases.
SrO *
So, the anions are distorted less.
BaO *
Covalent Character decreases
* Ionic Character increases
High
Polarisability of anions :
High polarisibility of anions is
the ease of distortion of the electron cloud of an anion
or
the ease with
which Anions responds to the polarising power of the cations.
Diagram:
Cations are able to distort the electron cloud of anions because there is a weaker attraction between outer electron shells and nucleus of anions. |
Polarisibility
of anions depends on size :
Polarisibility
of anions increases with increasing size.
Down
the Group7 ionic compounds ,
LiF * Charge
on the Anions remain same.
LiCl * Size of Anions increases .
LiBr *
Polarisibility of Anions increases.
LiI * So, the
anions are distorted more .
* Covalent
Character increases
*
Ionic Character decreases
Ionic character :
Ionic character
is the opposite of covalent character.
Cations with
greater size will have higher ionic character.
Anions with smaller
size will have higher ionic character.
This is because
of cations cannot distort the electron cloud.
When electron
distortion becomes weaker or impossible, then that compound would have high
ionic character and low covalent character.
Down the Group 1
ionic compounds ,
LiCl * Charge
on the cations remain same.
NaCl * Size of Cations increases .
KCl * Charge density of
cations decreases.
RbCl * So, the
anions are less distorted.
CsCl *
Covalent Character decreases
* Ionic
Character increases
Down the Group 2 ionic compounds ,
BeO * Charge
on the cations remain same.
MgO * Size of Cations increases .
CaO *
Charge density of cations decreases.
SrO * So,
the anions are less distorted .
BaO *
Covalent Character decreases
* Ionic Character increases
Down the Group7 ionic compounds ,
LiF * Charge
on the Anions remain same.
LiCl * Size of Anions increases .
LiBr *
Polarisibility of Anions increases.
LiI * So, the
anions are distorted more .
* Covalent
Character increases
* Ionic Character decreases .
Well, this is the end of today's post ! Follow me on this blog for getting updated with my posts like this. And you may get a video solution to a problem on this topic by the clicking the following link :
See you in the next post!! Bye Bye!!!
Sunday, 20 December 2015
Friday, 18 December 2015
Monday, 7 December 2015
Thursday, 3 December 2015
Wednesday, 2 December 2015
Tuesday, 1 December 2015
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