7.1 Ions

• To find the number of valence electrons in an atom of a representative element, simply look at its group number.
• Atoms of the metallic elements tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level. Atoms of some nonmetallic elements tend to gain electrons to achieve a complete octet.
• An atom’s loss of valence electrons produces a positively charged cation.
• The gain of electrons by a neutral atom produces negatively charged anion.

7.2 Ionic Bonds and Ionic Compounds

• Although they are composed of ions, ionic compounds are electrically neutral.
• Most ionic compounds are crystalline solids at room temperature, and they generally have high melting points. Ionic compounds can conduct an electric current when melted or dissolved in water.

7.3 Bonding in Metals

• The valence electrons of metal atoms can be modeled as a sea of electrons.
• Metal atoms are arranged in very compact and orderly patterns.
• Alloys are important because their properties are often superior to those of their component elements.