# Structure of [PCl4]+

Watch
Announcements
#1
Hi,

So i've done this aaages ago and couldnt find much help on the internet. I was asked to draw a dot and cross diagram of . Could any 1 help me with thatp lz?

Thanks.
0
10 years ago
#2
(Original post by wizz_kid)
Hi,

So i've done this aaages ago and couldnt find much help on the internet. I was asked to draw a dot and cross diagram of . Could any 1 help me with thatp lz?

Thanks.
Phosphorus is in group 5 = five valence electrons
Each chlorine (7 electrons) provides 1 electron to form a single bond = 4 electrons
But the species has a positive charge overall = -1 electron
---------------------------------------------------------

can you take it from there?
0
#3
(Original post by charco)
Phosphorus is in group 5 = five valence electrons
Each chlorine (7 electrons) provides 1 electron to form a single bond = 4 electrons
But the species has a positive charge overall = -1 electron
---------------------------------------------------------

can you take it from there?
Oh yes there is a dative covalent bond isnt there?

Thanks.
0
10 years ago
#4
(Original post by wizz_kid)
Oh yes there is a dative covalent bond isnt there?

Thanks.
You cannot dative coordinate to chlorine as it already has 7 electrons.
Chlorine cannot dative coordinate to phosphorus as that would not sort out it's outer shell of 7 electrons...

In brief, no.
0
#5
(Original post by charco)
You cannot dative coordinate to chlorine as it already has 7 electrons.
Chlorine cannot dative coordinate to phosphorus as that would not sort out it's outer shell of 7 electrons...

In brief, no.

Right. So would the right structure have P in the middle, covalently bonding to 4 chlorines. This would leave one electron in phosphorus' outer shell. Right? Now because this electron is not paired, is that the reason why the whole specie is +ve ?

Thakns.
0
10 years ago
#6
Structure is square planar if I remeber correctly?
0
10 years ago
#7
(Original post by piszczel)
Structure is square planar if I remeber correctly?
You remember incorrectly...
0
10 years ago
#8
(Original post by wizz_kid)
Right. So would the right structure have P in the middle, covalently bonding to 4 chlorines. This would leave one electron in phosphorus' outer shell. Right? Now because this electron is not paired, is that the reason why the whole specie is +ve ?

Thakns.
I'm afraid your maths is a little shaky:

Phosphorus = 5
Chlorines = 4
Positive charge subtract one electron
--------------------
total electrons = 8
--------------------
0
10 years ago
#9
(Original post by charco)
You remember incorrectly...
Well it has 8 electrons - 4 electron pairs... hmm tetrahedral?

This is worrying as I'm starting a chemistry course at uni in 2 weeks lol
0
10 years ago
#10
(Original post by piszczel)
Well it has 8 electrons - 4 electron pairs... hmm tetrahedral?

This is worrying as I'm starting a chemistry course at uni in 2 weeks lol
The only way to arrange four pairs of electrons (regions of charge density) is tetrahedral.
0
#11
(Original post by charco)
I'm afraid your maths is a little shaky:

Phosphorus = 5
Chlorines = 4
Positive charge subtract one electron
--------------------
total electrons = 8
--------------------
I get how it equals to +ve overall. However i'm still unclear about the unpaired electron.

Phosphorus has 5 electrons in its outer shell and 4 are bonded covalently with Cl. What happens to the 5th unpaired electron?

CHeers.
0
10 years ago
#12
(Original post by wizz_kid)
I get how it equals to +ve overall. However i'm still unclear about the unpaired electron.

Phosphorus has 5 electrons in its outer shell and 4 are bonded covalently with Cl. What happens to the 5th unpaired electron?

CHeers.

it is gone

it is an ex-electron

it is no longer there

vamoosh - disappeared

.. and for that reason the species has a positive charge.

The only way for a species to get a positive charge is to lose an electron.
0
#13
(Original post by charco)
it is gone

it is an ex-electron

it is no longer there

vamoosh - disappeared
Interesting. Is it because it is a free radical and reacts with (almost) anything that comes around?
0
10 years ago
#14
(Original post by wizz_kid)
Interesting. Is it because it is a free radical and reacts with (almost) anything that comes around?
It is a positive ion

You need to do some basic housekeeping...

Phosphorus (at no 15) has 15 protons and 15 electrons so overall it has no charge.

Each chlorine (at no. = 17) has 17 protons and 17 electrons, so overall no change

If you add up all of the protons in (hypothetical) PCl4 = 15 + 17 + 17 + 17 + 17 = 83+
If you add up all of the electrons in (hypothetical) PCl4 = 15 + 17 + 17 + 17 + 17 = 83-

So (hypothetical) PCl4 has a charge = +83 - 83 = 0

However PCl4+ has 1 positive charge. It cannot have gained a proton so ....

.... it must have lost an electron.

The electron can't be lost from a chlorine (as this would leave the Cl with only 7 in the valence shell), so it must have been lost from the Phosphorus valence shell.

Summary
--------
Phosphorus has four pairs of e's in its valence shell = tetrahedral.
1
#15
(Original post by charco)
It is a positive ion

You need to do some basic housekeeping...

Phosphorus (at no 15) has 15 protons and 15 electrons so overall it has no charge.

Each chlorine (at no. = 17) has 17 protons and 17 electrons, so overall no change

If you add up all of the protons in (hypothetical) PCl4 = 15 + 17 + 17 + 17 + 17 = 83+
If you add up all of the electrons in (hypothetical) PCl4 = 15 + 17 + 17 + 17 + 17 = 83-

So (hypothetical) PCl4 has a charge = +83 - 83 = 0

However PCl4+ has 1 positive charge. It cannot have gained a proton so ....

.... it must have lost an electron.

The electron can't be lost from a chlorine (as this would leave the Cl with only 7 in the valence shell), so it must have been lost from the Phosphorus valence shell.

Summary
--------
Phosphorus has four pairs of e's in its valence shell = tetrahedral.

At Alevel standard, do we just assume that the lost electron just disappears randomly?

Thanks for bearing with me
0
10 years ago
#16
(Original post by wizz_kid)
At Alevel standard, do we just assume that the lost electron just disappears randomly?

Thanks for bearing with me
It does not disappear randomly...

... in the same way as a sodium ion has a positive charge - it was lost at the moment of forming the ion.
0
#17
(Original post by charco)
It does not disappear randomly...

... in the same way as a sodium ion has a positive charge - it was lost at the moment of forming the ion.
Right! Thanks a lot for helping me through this mate. Really appreciate it.
0
10 years ago
#18
(Original post by wizz_kid)
Right! Thanks a lot for helping me through this mate. Really appreciate it.

No probs
0
10 years ago
#19
Did anyone mention it was tetrahedral?
0
10 years ago
#20
(Original post by chemicalguy)
Did anyone mention it was tetrahedral?

The thread went something like this...

(Original post by piszczel)
Structure is square planar if I remeber correctly?
(Original post by charco)
The only way to arrange four pairs of electrons (regions of charge density) is tetrahedral.
(Original post by charco)

Summary
--------
Phosphorus has four pairs of e's in its valence shell = tetrahedral.
yes, they did...
1
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### Poll

Join the discussion

#### Are you travelling in the Uni student travel window (3-9 Dec) to go home for Christmas?

Yes (107)
28.23%
No - I have already returned home (50)
13.19%
No - I plan on travelling outside these dates (71)
18.73%
No - I'm staying at my term time address over Christmas (39)
10.29%
No - I live at home during term anyway (112)
29.55%