Lead Pb

Discovery

Lead is easily smelted from its main ore, galena, so it was one of the first metals people produced. Ancient Rome made it on an industrial scale for water pipes, cookware and even a sweetener for wine, and Greenland ice cores record a clear rise in atmospheric lead during the Roman era.

In the twentieth century tetraethyllead added to petrol spread lead pollution across the globe. In 1956 the American geochemist Clair Patterson used lead isotopes in meteorites to calculate the age of the Earth as about 4.55 billion years. In the process he discovered how badly laboratories and the environment were contaminated with lead, and he became a leading campaigner against leaded petrol. The UN Environment Programme announced in 2021 that the last sales of leaded petrol, in Algeria, had ended.

Origin of the name

The symbol Pb comes from plumbum, the Latin word for lead. The English words plumber and plumb line share that root, because Roman water pipes were made of lead. The English word lead itself is of Germanic origin.

Main uses

• Lead-acid batteries: starter batteries for vehicles and backup power systems account for most lead used today, and they are among the most recycled products in the world.
• Radiation shielding: its density makes it ideal for X-ray room walls, protective aprons and shielding in nuclear facilities.
• Other uses: cable sheathing, fishing and diving weights, ammunition and some alloys. Electronics solder has largely switched to lead-free alloys under hazardous-substance rules.

Isotopes

Natural lead has four stable isotopes, 204, 206, 207 and 208, with lead-208 making up more than half. Lead-206, -207 and -208 are the end points of the decay chains of uranium-238, uranium-235 and thorium-232, so uranium-lead dating is the standard method for dating the oldest minerals on Earth. Lead-208 is doubly magic, with "magic" numbers of both protons and neutrons, which makes it especially stable. Radioactive lead-210 (half-life about 22 years) is used to date sediments laid down over the past century or so.

In everyday life

The World Health Organization considers that there is no known safe level of lead in the blood, and children are especially vulnerable to effects on learning and behaviour. Possible sources include flaking paint and dust in old buildings, old water pipes, and some imported cosmetics and pottery glazes. Wash your hands after handling fishing weights or batteries, and always return spent lead batteries for recycling.