Recheck
identify the molecular shape of each lewis structure.

bent
tetrahedral
trigonal planar
is this right

How to Tell Lewis Diagrams apart

Trigonal planar, Trigonal pyramid both have 3 things attached to them. Not 4. Tetrahedral is the only Lewis Diagram's center piece that has 4 things attached to it.

Tetrahedral: C with 4 Cl's attached.

Trigonal Planar: is flat. The element in the middle is generally a metal or an element from the Left side of the periodic table. There is never an isolated pair of electrons with Trigonal Planer shapes. Summary:

Trigonal Pyramid

Bent

Problem One

Both parts of this question are correct.

VSEPR theory and molecular shapes

The order is trigonal pyramidal, tetrahedral, trigonal planar, bent.

NI₃

NI₃ is trigonal pyramidal (see Figure 1).

Think of a trigonal pyramid as a three-legged stool, with the “central” atom (N) as the seat. The three iodine atoms form the feet of the stool.

If you close in all the sides of the figure, you have a trigonal (triangular) pyramid, i.e., a pyramid with a triangular base).

CCl₄

CCl₄ is tetrahedral (see Figure 2).

A tetrahedron is also a pyramid with a three-cornered base. The difference is that the central atom (C) is buried in the middle of the figure and all sides have the same length.

The three sides plus the base make four identical sides (tetra = four + hedra = faces) that are equilateral triangles.

BF₃

BF₃ is trigonal planar (see Figure 3).

It is flat, sort of like a slice of pizza. The three bonds point to the corners of an equilateral triangle.

NO₂⁻

NO₂⁻ is a bent molecule.

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Unit conversions

You want to convert miles per hour ⟶ kilometres per hour.

Convert miles to kilometres.

1 mi = 1.61 km                     Do the conversion.

99 × 1.61/1 = 160 km/h  

Convert hours to minutes.

1 h = 60 min                        Do the conversion

159 × 1/60 = 2.7 km/min  

Note: The answers can have only two significant figures because they all depend on the original speed (99 mph = two significant figures).  

in chemistry, adhesion and cohesion are attractive forces that exist between molecules. they hold the molecules together from each other. they are different in that adhesive force exists between molecules of different substance while cohesive force happens between molecules of same substance.

adhesion between water and glass causes water molecules at the edge of water and glass interface to climb up the wall in a narrow glass tube. this is called capillary action. cohesion is what gives glass its shape and causes water to form a droplet.