Читать книгу Geology For Dummies - Alecia M. Spooner - Страница 79

Each subatomic particle in an atom has a charge, similar to the way opposite ends of a battery or magnet are charged: positive or negative. In an atom, the protons are positive, the neutrons are neutral (no charge), and the electrons are negative. Most atoms have the same number of protons and electrons, which means the atom itself has no charge; it’s neutral.

When an atom with only one electron in its outer shell is near an atom with seven electrons in its shell, the single electron will jump over to join and complete the almost-full shell. This action results in the first atom having one more proton than electrons and, therefore, a positive (or +1) charge. Meanwhile, the second atom has one more electron than protons and, therefore, a negative (or –1) charge. (Later in the chapter, Figure 5-4 illustrates this fact.)

Atoms or molecules (more than one atom joined together) with positive or negative charge are called ions. The charge of the ion is determined by how the electrons in its outer shell move to and from nearby atomic shells. An atom with a positive charge is called a cation, and an atom with a negative charge is called an anion. Atoms, and even compounds, can have negative charges of 1, 2, 3, and even 4 (though 4 is rare) and positive charges up to +8. The interaction of ions with one another is one way that atoms form bonds; keep reading to find out the details.