Shapes of Molecules?

Question

This an online assignment I have gotten wrong twice. Help is appreciated, thanks!

What is the shape of each molecule below? Select the correct answer. Answers can be used more than once.

 linear bent/v-shape trigonal planar trigonal pyramidal tetrahedral trigonal bipyramidal see-saw T-shape octahedral square pyramidal square planar  KrF₂

 linear bent/v-shape trigonal planar trigonal pyramidal tetrahedral trigonal bipyramidal see-saw T-shape octahedral square pyramidal square planar  ClF₃

 linear bent/v-shape trigonal planar trigonal pyramidal tetrahedral trigonal bipyramidal see-saw T-shape octahedral square pyramidal square planar  SF₄

 linear bent/v-shape trigonal planar trigonal pyramidal tetrahedral trigonal bipyramidal see-saw T-shape octahedral square pyramidal square planar  XeF₄

 linear bent/v-shape trigonal planar trigonal pyramidal tetrahedral trigonal bipyramidal see-saw T-shape octahedral square pyramidal square planar  SF₆

 linear bent/v-shape trigonal planar trigonal pyramidal tetrahedral trigonal bipyramidal see-saw T-shape octahedral square pyramidal square planar  AsF₅

 linear bent/v-shape trigonal planar trigonal pyramidal tetrahedral trigonal bipyramidal see-saw T-shape octahedral square pyramidal square planar  IF₅

Answer 1

Hello He. I'll give you a hint on this question. To determine how many atoms we need, look at the periodic table.

1. KrF2: Kr is in the last column so it has 8. F is in the second to last column so it has 7. 8+(7*2)=22. This one is an exception to the rule that only 8 atoms can be on each atom-Kr has 10. Therefore, there are 2 lone pairs (atoms that are not bonded to F). The steric no. = (# of atoms bonded to central atom-Kr) + (# of lone pairs on central atom). There are 2 pairs of atoms bonded to Kr + 3 lone pairs=5. Linear should be your answer.
2. ClF2: Cl and F both have 7 atoms. Therefore the total is 7 + (7*2)=21. However, we can't have an odd number of atoms so we must give this structure a negative charge, which increases the counts one. When we draw it out there are 3 lone pairs on Cl. Steric no= 2 + 3=5