Four different substituents are required on a carbon atom for it to be chiral.
<h3>What is Chiral Carbons ?</h3>
The carbon atom which is attached with four different types of group of atoms or atoms is called Chiral carbon. Chiral molecules are non superimposable on their mirror images. Chiral carbon is also called asymmetric carbon.
Example:

In the above example we can see that carbon atom has 4 different group attached with it that is Br, Cl, H, CH₃.
Thus from the above conclusion we can say that Four different substituents are required on a carbon atom for it to be chiral.
Learn more about the Chiral carbon here: brainly.com/question/1195366
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Answer:
B. Distributed over a very wide range
D. Limited life existence in geologic time.
Explanation:
Index fossils are very unique fossils that helps in determining the relative ages of rocks and biostratigraphic correlation. They are usually called guide fossils.
- Fossils are the preserved remains of dead organisms found in rocks.
- Index fossils are a special class of fossils with the following properties;
- They are widely distributed.
- They have a short stratigraphic range.
- They show rapid evolution trends
One lone pair, as there is a single covalent bond between the hydrogen and the carbon, and a triple covalent bond between the nitrogen and the carbon, leaving two free electrons/one electron pair on the nitrogen..... I think ((:
2.4 mol NaSO2 × (6.02×10^23) f.units ÷ 1 mol
=1.44480000×10^25
Approximately 1.4×10^25, if you use sig.figs.