Answer -C They are defined by the number of electrons.
An orbital is a function that describes the probability of finding the electron with certain energy at certain distance from the nucleus therefore, it is defined by the number of electrons.
Answer:
Solutions from highest to lowest freezing point:
0.040 m glycerin = 0.020 m potassium bromide > 0.030 m phenol
Explanation:

= Depression in freezing point
i = van'T Hoff fcator
= Molal depression constant of solvent
m = molality of the solution
Higher the value of depression in freezing point at lower will be freezing temperature the solution.
1. 0.040 m glycerin
Molal depression constant of water = 
i = 1 ( organic molecule)
m = 0.040 m


2. 0.020 m potassium bromide
Molal depression constant of water = 
i = 2 (ionic)
m = 0.020 m


3. 0.030 m phenol
Molal depression constant of water = 
i = 1 (organic)
m = 0.030 m




Solutions from highest to lowest freezing point:
0.040 m glycerin = 0.020 m potassium bromide > 0.030 m phenol
<span>Answer:
3 electron pairs
Let's take BF3 for an example.
When you find the valence electrons for this molecule --> [3+(3x6)], you'll get 24e-. You draw the Lewis dot structure and each of the F atom would have six dots around it (a total of 18 because there's 3 F atoms) and the B would have three lines [one line attached to each F. One line would equal to 2 valence electrons] and you get a total of 24 valence e-.
The question asks how many groups are on the CENTRAL atom, meaning on the B. It would be three</span>