Lead is a relatively poor conductor of electricity; it is highly resistant to corrosion, but tarnishes on contact with air. Isotopes of lead are the end product of decay in each of three series of naturally occurring radioactive elements.
John Dalton (1766-1844) in A New System of Chemical Philosophy, published in 1808, revived the atomic theory of matter, adding to it the key idea that different elements had different characteristic atomic weights. He also proposed a system of arbitrary marks for several elements, thus moving on from the alchemical / chemical symbols of Karl Wilhelm Scheele (1742-1786). Lead is represented by the letter L inside a circle.