What is the bond angle of H20

Similar to the water molecule, the hydrogen sulfide molecule is also angled.
Although the formulas of hydrogen sulfide and hydrogen are similar, the substances have completely different properties. So is z. B. hydrogen sulfide a gas at room temperature. Apparently it has little tendency to form hydrogen bonds. What is the cause of this?
Consequently, dipole forces should also occur with hydrogen sulfide. However, these are lower than with water. The reason for this is that the electronegativity (EN) of sulfur (2.58) differs only slightly from that of hydrogen (2.20). The EN difference is very small at 0.38. Therefore, the electrons are not shifted significantly towards the sulfur, the molecule has hardly any dipole properties.
It is different with water: Here the EN difference between oxygen and hydrogen is 1.24.

Molecules of H2O and from H2S.

Something else is striking: The bond angle of H2At 92.3 , S is smaller than that of the water molecule. One can say that the H atoms in the H2Include a right angle. In the case of the water molecule, the bond angle is 104.5 . This corresponds to the interior angle of a tetrahedron.

The difference: in the water molecule, the orbitals are sp3-hybridized - so there is a tetrahedron.
In the sulfur atom (unlike the oxygen in water) the s and p orbitals are only slightly hybridized. The three p orbitals are at right angles to each other.

Here is a comparative look at the electronic structures.

First of all the Oxygen and the water:

The hydrogen pushes its electrons into the two half-full p orbitals (shown in red). At the same time there is a hybridization to 2sp3 instead, because all electrons (2s and 2p) are strongly drawn to the oxygen atom. The 2sp3-Orbitals are the non-bonding (free) electron pairs.

Now for the Sulfur and hydrogen sulfide:

The hydrogen pushes its electrons into the two half-full 3p orbitals (shown in red). The 3s and 3p orbitals filled in from the beginning form non-bonding electron pairs.

A hybridization to 3sp3 does not take place. Due to the high nuclear charge of the sulfur atom, the 3s electrons are drawn to the nucleus and evade hybridization. In addition, the deflection of the 3p orbitals is too great, the electrons in them are not so strongly drawn to the sulfur atom and hybridization does not result in any significant energy gain.

Now we also understand why there is an H under normal conditions3O+-Ion, but no H3S.+-Ion there. Unlike the tetrahedral orbitals in the water molecule, the orbitals that are perpendicular to one another would be in the H2Repel S molecule too strongly.


Further texts on the subject of `` sulfur ''