Counting Atoms Practice

Front

What is the definition of an element in chemistry?

Back

An element is a pure substance that cannot be broken down into simpler substances by chemical means. It consists of atoms that all have the same number of protons.

Front

How do you determine the number of elements in a chemical formula?

Back

Count the different capital letters in the formula. Each capital letter represents a different element.

Front

What does the subscript in a chemical formula indicate?

Back

A subscript indicates the number of atoms of the element that are present in the molecule. For example, in H2O, the '2' indicates there are two hydrogen atoms.

Front

In the formula C8H10N4O2, how many total atoms are present?

Back

24 atoms (8 carbon + 10 hydrogen + 4 nitrogen + 2 oxygen).

Front

What is the formula for calculating the total number of atoms in a molecule?

Back

Add the number of atoms of each element together, as indicated by the subscripts in the chemical formula.

Front

How many atoms are in one molecule of O2?

Back

2 atoms (since O2 has a subscript of 2 for oxygen).

Front

What is the significance of the coefficient in a chemical formula?

Back

A coefficient indicates how many molecules of the compound are present. For example, in 5N2O, there are 5 molecules of N2O.

Front

How many nitrogen atoms are in 5N2O?

Back

10 nitrogen atoms (5 molecules x 2 nitrogen atoms per molecule).

Front

What is the difference between a molecule and an atom?

Back

An atom is the smallest unit of an element, while a molecule is a group of two or more atoms bonded together.

Front

How many elements are in the compound N2O?

Back

2 elements (nitrogen and oxygen).