We use a variety of counting units for different objects in daily situations.
For example, when you hear the word, "dozen," you probably think of a quantity of 12. If you were buying eggs, you probably wouldn't ask for 12 or 24. Instead you would ask for one or two dozen. This fixed quantity can be applied to counting just about anything, including roses or doughnuts.
Similarly, when you hear the word "pair," you probably think of a quantity of two. A pair is always two items, whether these items are shoes, gloves, or earrings. So when you think about the quantity of shoes you own, you likely think about the number of pairs you own instead of the number of individual shoes.
While the pair and dozen are useful counting units for a small number of items, chemists need a more practical unit for counting things like the number of atoms. In this lesson, you will learn about a special unit used by chemists to express amounts of particles, such as atoms and molecules. You will also learn how to use this set quantity to solve problems related to the mass of a substance in grams.
Question
Consider the fact that there are about 5 \( \times \) 1017 atoms of neon present in each breath you inhale. Why is it useful to have a special unit for working with these small particles?
We need a large counting unit because atoms are so small that even in a small sample, it's impossible to count them.
