Group 16- The Chalcogens Flashcards
What is the outer electron configuration?
ns2np4
Describe the trend in metallic character
Metallic character increases as the group descends
What is the highest oxidation state?
+6
What species do they like to form?
X2-
Describe the 1st and 2nd electron gain enthalpy?
The 1st is exothermic and the 2nd is endothermic
However energy is received back from the formation of ionic or covalent bonds
Describe the boiling points from H2S to H2Se
The boiling points increase due to greater van der waals forces
Why is the boiling point of H2O high?
It is high due to hydrogen bonding
Why is does SF6 break the octet rule?
S has 6 electrons and each f donates an electron
In total there are 12 valence electrons which breaks the octet rule?
Why is SF6 unreactive with water?
The f shields s from attack
What is the synthesis of SF6?
S8 + 24F2 -> 8SF6
What are the properties or SF6?
\+6 oxidation state Colourless Odourless Inert Non toxic Non flammable Breaks octet rule
Describe the geometry of SF6
6 bonding pairs so it is octahedral
Sp3d hybridisation is a poor way of account for its hyper valency
Describe the orbitals involved in bonding for SF6
S has 3s, 3pxyz
Each f uses a single p orbital
That means there are 10AO and so therefore 10 molecular orbitals
Describe the MO that make up the bonding in SF6
10 AO means there are 10 MO
4 are bonding
4 are antibonding
2 are non bonding
How are the bonding orbitals formed in SF6?
A bonding MO is made with the f p orbitals and the S 3s orbital all in phase with each other
3 degenerate bonding MOs are made with the p orbitals of f and the 3 x3p orbitals of S being in phase with each other
How are the antibonding orbitals made in SF6
An antibonding MO is made with the f p orbitals being in the same phase as the bonding MO but the S 3s is now out of phase with these
3 more antibonding MO are made with the f p orbitals being in the same phase as the bonding MO but the S 3x 3p is now out of phase with these
How do you calculate bond order?
BO= (Bonding- antibonding)/2
What is the bond order of SF6?
8-0/2 =4
This is spread over all 6 F= 2/3
No electrons occupy antibonding
8 electron will occupy bonding, 4 will occupy non bonding
How does the MO orbitals explain the hypervalency in SF6?
8 electrons occupy bonding
4 electrons occupy non bonding
This means 8 of the 12 electrons occupy bonding so the octet rule still applies and the molecule can exist
Why is SBr6 unknown when we have SF6?
Four electrons are placed entirely on electronegative fluorine atoms so it is stabilised
Br isn’t as electronegative
S-F bonds may be stronger
How are the non bonding MO orbitals made?
There is no contribution from S, these are entirely based on F
