Question

Number of planar atoms in SF6?
Number of possible isomers of formula C7H8O?
If l=3 for an atom then no.of orbitals in outer shell are?

Answer 1

SF6 - sulfur hexa floride has six sulfur - floride single bonds.  Sulfur is at the center and 6 florine atoms are equally distributed in space ALL neighboring bonds being perpendicular to one another.

It is a octahedral structure.   There are 4 planar  florine and 1 sulfur : 5 total in one plane.
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there are  5 isomers for  phenyl methanol  C7 H8 O:  C6 H4 CH3 OH
 
1.    2- methyl phenol 
    In the hexagonal benzene ring,  you have C-H at 4 vertices.  Then at the 5th one you have  C-CH3   and at the sixth  OH.    CH3 and OH groups are attached to Carbons which are adjacent to each other in the ring.

2.   3-methyl  phenol

    the CH3 and OH groups are attached to carbons in the ring, that are separated by 1 carbon in the middle.

3.  4- methyl phenol
    the CH3 and OH groups are attached to carbons opposite to each other in the benzene ring.

4.  methoxy benezene
     group OCH3 is attached to one carbon in the benzene ring.   O bonds with Carbon in the ring.

5.  phenyl methanol
     The group CH2-OH  is attached to one carbon in the benzene.  C bonds with carbon in the ring.
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is it for  n = 3  or  l = 3 ?
if it is n = 3 ,  principal quantum number , then  there are s, p and d orbitals in the shell. 1 s , 3 p and 5 d orbitals.
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Is that  l = azimuthal quantum number ?
 l = 0   means  the   orbital or sub shell   s
l = 1     =>  p orbital 
l = 2   =>  d  orbital 
l = 3    =>  f orbital  
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In a shell , with n as the principal quantum number,  we have many orbitals or sub shells with the above  azimuthal quantum number  l.

there are  (2 l + 1) number of orbitals of type l.  
Hence there are  1 orbital of type s.  3 of type  p.  5 of type  d.  7 of type f.   A one orbital contains a pair of electrons,  the capacities of orbitals are:  s = 2 electrons, 3 p orbitals have 6 electrons.  5 d orbitals contain 10  electrons in total.   7 f orbitals have 14 electrons.