Question

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1. In your own words, what is the difference between a molecule's electron geometry and its molecular geometry? 2. Building on the last question, why does ammonia have a tetrahedral electron geometry but a trigonal pyramidal molecular geometry? 3. Why do the atoms in a carbon dioxide molecule arrange themselves into a linear molecular geometry (instead of, for example, a bent one)? Why do the atoms in a water molecule arrange themselves into a bent geometry (instead of, for instance, a linear geometry like carbon dioxide)? In other words, what causes the atoms to arrange themselves this way? 5. Why is CH2Cl2 polar while CH4 and CCl4 are both non-polar?

Please No Cursive Please hard to read

Answer 1

ANSWERS

1.in simple words electron geometry includes lone pair of the central atom while molecular geometry considers only the bond pairs .it means that for electron geometry lone pairs are considered similiar to that of bond pair and the electron geometry includes both lone pairs of the central atom as well as bond pairs.

2.NH3 ( AMMONIA) Has central atom nitrogen with 5 valence electrons .3 of them are bonded with H atoms and two are left as a lone pair .so there are total 4 units that include three bond pairs and a lone pair .so all units are to be considered for electron geometry hence it has tetrahedral electron geometry.while for molecular geometry only 3 bond pairs are to be considered hence it has pyramidal molecular geometry.

3.molecule always tend to have maximum stability and minimum repulsion so for co2 it is only possible if the two O atoms are farthest apart from each other which will be possible only if the two atoms (O ATOMS) are 180 degree apart.hence they have linear geometry.in case of bent one the two O atoms will be near to each other causing repulsions between bond pairs leading to instability.

4.in case of water molecule the central atom is O atom .it has 6 valence electrons .two of them are bonded to H atoms while 4 electrons are left as two lone pairs .now lone pair-lone pair repulsions are much stronger than lone pair - bond pair repulsions which is stronger than bond pair-bond pair repulsions.so the lone pairs repeal each other as well as bond pairs to be in a state of minimum repulsion and maximum stability.hence they push the bond pairs to get themselves as apart from each other (lone pairs). causing a bent structure.

5.a simple reason to explain this is that in CH2Cl2 there are two type of bonds C-H and C-Cl .both the H and Cl atom have different electronegativities hence both have different extent of dipoles causing a net dipole moment in the molecule causing the molecule to be polar.while ch4 and ccl4 all similar atoms so the dipoles get cancelled causing a net zero dipole moment .hence molecule is non polar.