Final answer:
There are 90 chemical elements, composed of nearly 100 different types of atoms, that occur naturally on Earth. These elements include 81 with stable isotopes and constitute the diverse forms of matter we encounter.
Step-by-step explanation:
On Earth, there are 90 chemical elements, which are composed of different types of atoms. These chemical elements include 81 that have at least one stable isotope. A substance that is made up of only one type of atom is called an element. One example provided was chlorine, which has two main natural isotopes, those with a mass number of 35 and 37.
The variety of elements come in both plentiful and rare forms, and while 118 different types of atoms have been identified, only a few of them make up the majority of matter we encounter regularly. Interestingly, it's estimated that nearly 100 different kinds of atoms exist in nature, contributing to the diverse materials and technologies we use, such as cell phones, which almost one-third of natural elements are used to create.