Читать книгу Earth Materials - John O'Brien - Страница 43

The periodic table not only organizes the elements into rows based on their electron properties, but also into vertical columns based upon their tendency to gain or lose electrons to become more stable (Table 2.3). Ideal atoms are electrically neutral because they contain the same numbers of positively charged protons and negatively charged electrons (p⁺ = e⁻). Many atoms are not electrically neutral; instead they are electrically charged particles called ions. The process by which they acquire their charge is called ionization (Box 2.1). In order for an ion to form, the number of positively charged protons and negatively charged electrons must become unequal. Cations are positively charged ions because they have more positively charged protons than negatively charged electrons (p⁺ > e⁻). Their charge is equal to the number of excess protons (p⁺ − e⁻). Cations form when electrons are lost from the electron cloud. Ions that have more negatively charged electrons than positively charged protons, such as the ion chlorine (Cl⁻ ), will have a negative charge and are called anions. The charge of an anion is equal to the number of excess electrons (e⁻ − p⁺). Anions form when electrons are added to the electron cloud during ionization.