Chapter 6 Ionic and Molecular Compounds 6.1 Ions: Transfer of Electrons Learning Goal Write the symbols for the simple ions of the representative elements.

Chapter 6 Readiness Key Math Skills Using Positive and Negative Numbers in Calculations (1.4B) Solving Equations (1.4D) Core Chemistry Skills Writing Electron Configurations (5.4) Drawing Electron-Dot Symbols (5.6)

Compounds Most elements except for noble gases are found in nature combined with other elements in compounds. Compounds form when electrons are transferred or shared to give a stable electron configuration to both atoms.

Compounds Atoms lose, gain, or share electrons in the form of an ionic bond or covalent bond to obtain an octet. Ionic bonds are formed when the valence electrons of a metal are transferred to atoms of nonmetals. Covalent bonds are formed when atoms of nonmetals share their valence electrons.

Ionic and Molecular Compounds

Ionic and Molecular Compounds

Positive Ions: Loss of Electrons Ions, which have electrical charges, form when atoms lose or gain electrons to form a stable electron configuration. Because ionization energies of metals in Group 1A (1), 2A (2), and 3A (13) are low, metal atoms lose their valence electrons, forming ions with a positive charge.

Positive Ions: Loss of Electrons A sodium atom (Na) will lose its 3s1 electron to form a sodium ion (Na+). Positively charged ions of metals are called cations.

Positive Ions: Loss of Electrons Magnesium, a metal in Group 2A (2), obtains a stable electron configuration by losing two valence electrons, forming an ion with a 2+ charge.

Negative Ions: Gain of Electrons The ionization energy of a nonmetal atom in Groups 5A (15), 6A (16), and 7A (17) is high. Rather than lose electrons to form ions, a nonmetal atom will gain one or more electrons to obtain a stable electron configuration.

Negative Ions: Gain of Electrons An atom of chlorine with seven valence electrons gains one electron to form an octet. Because it now has 18 electrons and not 17 electrons, it becomes a chloride ion (Cl−) with a charge of 1−. Negatively charged ions of nonmetals are called anions.

Formula and Names of Some Common Ions

Learning Check Select the correct answer for aluminum. A. The electron change to obtain an octet is _____. (1) loss of 3 e− (2) gain of 3 e− (3) gain of 5 e − B. The charge of the aluminum ion is _____. (1) 3− (2) 5− (3) 3+ C. The symbol for the aluminum ion is _____. (1) Al3+ (2) Al3– (3) Al+

Solution Select the correct answer for aluminum. A. The electron change to obtain an octet is _____. (1) loss of 3 e− B. The charge of the aluminum ion is _____. (3) 3+ C. The symbol for the aluminum ion is _____. (1) Al3+

Ionic Charges from Group Numbers We can use group numbers of representative elements in the periodic table to determine their charges. Group Number Ion Charge Group 1A (1) 1+ Group 2A (2) 2+ Group 3A (13) 3+ Group 5A (15) 3− Group 6A (16) 2− Group 7A (17) 1−

Common Ions and Their Nearest Noble Gases Atoms lose or gain electrons to become like their nearest noble gas.

Learning Check Select the correct answer for sulfur. A. The group number for sulfur is _____. B. The number of valence electrons in sulfur is ____. C. The change in electrons for an octet requires a (1) loss of 2 e− (2) gain of 2 e− (3) gain of 4 e− D. The ionic charge of a sulfide ion is _____. (1) 2+ (2) 2− (3) 4−

Solution Select the correct answer for sulfur. A. The group number for sulfur is 6A (16). B. The number of valence electrons in sulfur is six. C. The change in electrons for an octet requires a (2) gain of 2 e− D. The ionic charge of a sulfide ion is _____. (2) 2−

Chemistry Link to Health, Ions Several ions in body fluids have important physiological and metabolic functions.