# Why NH3 is arranged as a tetrahedron

why NH3 is arranged as a tetrahedron rather than arranged like the earth(N) is surrounded by 3 satellite(H)?

O=C=O

If is +ve, then it is repelled at its position but it will be attracted if it is at the position of .
Why CO2 is still considered as a non-polar molecule?
is exactly above the C

primarygun said:
why NH3 is arranged as a tetrahedron rather than arranged like the earth(N) is surrounded by 3 satellite(H)?

Molecular orbitals require that electrons be found in certain places. The "mini solar system" model of the atom (the Bohr model) does not explain covalent bonding.

http://chemlabs.uoregon.edu/GeneralResources/models/vsepr.html

primarygun said:
O=C=O

If is +ve, then it is repelled at its position but it will be attracted if it is at the position of .
Why CO2 is still considered as a non-polar molecule?
is exactly above the C

It is not considered to be non-polar, it is non-polar.

a polar molecule is one in which you find an asymmetric charge distribution that gives rise to dipoles on the molecule. there is no such region of electron density on $CO_2$

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Thank you.
so the method to find out whether a molecule is non-polar or polar is to draw axis of symmetry on it.
Does this method always work? If not, please tell me what the limitation is.