Which of the following molecules are linear?

BF3
HN3
COS
NH3
O3
SiF4
AsH3
SO2
C2H2
PF3
CF4
H2O
SO3
HCN
N2O
H2S
CS2

After drawing out all the lewis structures, and using VSPER theory, I found: COS, C2H2, CS2, HCN to be linear.
Am I right/missing any?

Yes, you are correct in identifying COS, C2H2, CS2, and HCN as linear molecules. These molecules have a linear molecular geometry according to the VSEPR (Valence Shell Electron Pair Repulsion) theory.

To determine the molecular geometry, you can follow these steps:
1. Draw the Lewis structure of the molecule, representing the bonding and lone pairs of electrons.
2. Determine the total number of electron groups, which includes both bonding and lone pairs.
3. Determine the electron group arrangement by applying VSEPR theory, which states that electron groups repel each other and tend to be as far apart as possible.
4. Identify the molecular geometry based on the electron group arrangement.

Let's go through the given molecules one by one to identify their molecular geometries:

1. BF3: Boron trifluoride has a trigonal planar geometry (not linear) as it has three bonding pairs and no lone pairs.
2. HN3: Hydrazoic acid has a linear geometry (linear) as it has three bonding pairs and no lone pairs.
3. COS: Carbonyl sulfide has a linear geometry (linear) as it has two bonding pairs and no lone pairs.
4. NH3: Ammonia has a trigonal pyramidal geometry (not linear) as it has three bonding pairs and one lone pair.
5. O3: Ozone has a bent geometry (not linear) as it has two bonding pairs and one lone pair.
6. SiF4: Silicon tetrafluoride has a tetrahedral geometry (not linear) as it has four bonding pairs and no lone pairs.
7. AsH3: Arsine has a trigonal pyramidal geometry (not linear) as it has three bonding pairs and one lone pair.
8. SO2: Sulfur dioxide has a bent geometry (not linear) as it has two bonding pairs and one lone pair.
9. C2H2: Acetylene has a linear geometry (linear) as it has two bonding pairs and no lone pairs.
10. PF3: Phosphorus trifluoride has a trigonal pyramidal geometry (not linear) as it has three bonding pairs and one lone pair.
11. CF4: Carbon tetrafluoride has a tetrahedral geometry (not linear) as it has four bonding pairs and no lone pairs.
12. H2O: Water has a bent geometry (not linear) as it has two bonding pairs and two lone pairs.
13. SO3: Sulfur trioxide has a trigonal planar geometry (not linear) as it has three bonding pairs and no lone pairs.
14. HCN: Hydrogen cyanide has a linear geometry (linear) as it has two bonding pairs and no lone pairs.
15. N2O: Nitrous oxide has a linear geometry (not linear) as it has two bonding pairs and one lone pair.
16. H2S: Hydrogen sulfide has a bent geometry (not linear) as it has two bonding pairs and two lone pairs.
17. CS2: Carbon disulfide has a linear geometry (linear) as it has two bonding pairs and no lone pairs.

So, in addition to COS, C2H2, CS2, and HCN, you can also include HN3 as a linear molecule.