Molecular geometry:

Molecular geometry is defined as the three dimensional arrangement of atoms that constitutes a molecule. Molecular geometry includes a general structure of molecules with bond lengths, torsional angles and bond angles along with other geometrical parameters that helps in determining the position of each of the atoms. Several other properties that are included under the molecular geometry includes reactivity, polarity, biological activity, phase of matter, magnetism etc. The angles that are formed between the bonds of atoms depend on the molecule and their transferable properties. Molecular geometry can be determined by various methods such as spectroscopic methods, diffraction, microwave, Raman spectroscopy that helps in giving information about the geometry of the molecule. This information includes details of the vibrational and rotational absorbance that are detected by the technique of X ray crystallography, neutron diffraction and many more. Al these helps in giving a molecular structure to the crystalline solids that are based on the distance between the nuclei and the concentration of the density of the electron. Thus it can be said that molecular geometry is the name that is given to geometry that are used to describe the shape of central terminal atom with in a compound. The VSEPR model though considered to be a model n determining the shape of the molecular geometry but still it is not a type of perfect model that is used in determining so. The VSEPR model is a type of system that helps in explaining the shapes of the known molecular geometry shapes that are discovered in experiments. This allows prediction of the geometry figures that are similar to the molecules.

Example:

One of the examples of molecular geometry is Water. The molecular geometry figure of Water results from the tetrahedral electron pair geometry. The molecule of watter is very common to memorize and consist of a bent molecular geometry.

In H20, the oxygen has about 6 valence electrons and hence needs 2 more electrons in order to complete its octet. In this situation, two electrons from the hydrogen atom leaves to another atom. The two hydrogen atoms and the two electrons pairs then falls apart at an angle of 109 degree bond angle. This gives rise to tetrahedral electron pair geometry. The two electron pair then exerts an extra repulsion on the two bonding atoms of hydrogen while creating a compression to the bond angle of 104 degree bond angle.  The water molecule forms a bent geometry figure as the lone electron pairs exerts pressure on the shape while forming the molecular geometry.

Steps that are followed while finding out the shape of the molecule includes-

1. Drawing the Lewis Structure.

2. Counting the number of electron groups and identifying them as the bond pairs of electron groups or the lone pairs of electrons including the bonds and the lone pairs.

3. Naming the geometry of the electron groups

4. By positioning the atomic nuclei around the molecular geometry.

The molecular geometry of atoms can be explained with the change in bonds . In order to predict the geometry of molecule a reasonable Lewis structure is written based on the molecule. The number of bonding and non-bonding pairs of electrons on the central of the atom is determined while forming the molecular structure of atoms. Systematically, five basic electron pair geometries can be formed based on the variation of the molecular geometries that can occur such as two electron pair, three electron pair, four electron pair, five electron pair and sic electron pairs. The two electron pair molecular structure is known as linear, the three electron pair is known as trigonal planar, the four electron pair is known as tetrahedral, the five electron pair model is known as trigonal bi-pyramidal, while the six electron pair is known as octahedral.

Causes of molecular geometry:

Electron pairs of a molecule are bonded with each other with the help of covalent molecules. As these electron pairs are mutually negatively charged, the electron pairs repel the other electron pairs while causing to move as far apart in order to stabilize the molecules. Thus this effect of repulsion is the major cause for the building up of molecular geometry having distinct shapes.

Difference between electron geometry and molecular geometry:

Whenever atoms forms a bond to the central atom in order to form a molecule, it tends to do it while maximizing the distance between the bonded electrons. This process gives the molecules a particular shape consisting of zero lone pairs of electrons. A lone pair is a set of two valence electrons that do not get shared among the bonding atoms. Lone pairs occupy more space than eh bonding electrons while causing the total effect to bend the shape of the molecule. In absence of non-bonding electrons, the shape of the molecules and electrons remains the same. Linear electron geometry involves all the central atom having two pairs of bonding electrons at an angle of 180 degree. One of the examples of molecule with linear shape of molecule is carbon dioxide or CO2. Thus the difference between molecular geometry and electron geometry are stated as follows:

Electron geometry forms the shape by electrons while taking them around the central atom. In electron geometry, these electrons form geometry either of the chemical bond or in terms of lone pairs. Electron geometry can be of different types such as linear, tetrahedral, Octahedral, Trigonal Bi-pyramidal and many more.

Whereas in molecular geometry the molecular shapes are formed in actual connection between the atoms in a compound. The shape of the electron geometry is scaffold and the connections between the atoms depend on the scaffolds. Ammonia has an electron geometry of tetrahedral that is it consists of 4 electrons around the central atom. The electron geometry of Ammonia has a lone pair which when put at the top it forms a connection between the N-H (3 of them) making a compound of NH3 which looks similar to that of the camera of a tripod and forms a molecular geometry of Trigonal Pyramidal.

The number of total electron pairs is calculated in electron geometry but the total numbers of electron pairs are not calculated in case of molecular geometry.

With the help of electron geometry, the spatial arrangements of the lone pairs are possible along with the bond in the molecule. With the help of this type of arrangement, it is possible to determine the electron domains that are repelling each other with the help of the VSEPR theory.

Electron geometry is the shape of a molecule that is predicted while considering the bond of both the electron pairs and the lone pairs. While in case of molecular geometry, the shapes of the molecule are predicted considering the bond of the electron pairs.

Molecular geometry of cli5:

In Chlorine Penta-iodide the cluster is said to be the smallest hyper lithiated cluster that was observed to be having two different molecular geometries degenerating energies but having C4V and D3h. The structure of C4 is square pyramidal with an associated base containing four lithium atoms in a plane while the carbon atom is slightly above the plane with the fifth Li atom at its apex. The binding energy of this state is about -10.0244 eV, with a dipole moment of 0. 58 D. The ionization potential of CLi5 is about 3.87 eV which is almost close to the calculated value of 3.902 eV The electron affinity is about 0.69 eV and is calculated by using the ground state of the anion which is in the C4 structure.