Читать книгу Geology For Dummies - Alecia M. Spooner - Страница 80

Very few atoms exist in nature all by themselves. Multiple atoms joined together are called molecules. Some atoms of the same element pair up with each other to form molecules. An example of this is oxygen gas, which is composed of two oxygen atoms, written as O₂. (The small 2 indicates how many atoms of oxygen are in the molecule.)

In other cases, atoms of two or more different elements combine to form a compound. The compound is held together by a chemical bond. In this section, I explain the three most common types of chemical bonding between atoms.

How two atoms bond together is determined by the number of electrons in their outer orbital shells. For example, an atom with 13 total electrons such as aluminum (Al) will have two electrons in the first orbital shell, eight electrons in the second orbital shell, and three electrons in the outermost orbital shell. The three electrons in the outermost shell are the ones that participate in bonds with other atoms.