II.

Properties of Lead

Metallic lead is a soft, malleable, ductile metal. When gently heated it can be forced through annular holes or dies. It has low tensile strength and is a poor conductor of electricity. A freshly cut surface has a bright silvery luster, which quickly turns to the dull, bluish-gray color characteristic of the metal. Lead melts at 327.46°C (621.43°F), boils at 1749°C (3180°F), and has a specific gravity of 11.35; the atomic weight of lead is 207.2.

Lead is soluble in nitric acid but is little affected by sulfuric or hydrochloric acids at room temperature. In the presence of air, it slowly reacts with water to form lead hydroxide, which is slightly soluble. Lead is toxic when taken internally; although ordinary water usually contains salts that form a coating on pipes, inhibiting the formation of soluble lead hydroxide, pipes used for carrying drinking water should not contain lead.

Lead occurs naturally in eight isotopic forms, of which four are stable and four are radioactive. The stable isotopes, lead-206, lead-207, and lead-208, are, respectively, the end products of the uranium, actinium, and thorium series of radioactive decay; lead-204, also stable, has no natural radioactive precursors (see Radioactivity).