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H' at. wt. (natural) 1.007967
   at. wt. (H') 1.007822
   at. no. 1
   m.p. - 259.140C
   b.p. - 252.870C 
   density 0.08988 gm./l
   density (liquid) 70.8 gm/i. (-2530C)
   density (solid) 7016 gm/i. (-2620C)
   valence 1.

**Electronic configuration**
K	L	M	N	O	P	Q
1	2	3	4	5	6	7
s	s p	s p d	s p d f	s p d f	s p d f	s p d f
1

LEAD (Anglo-Saxon lead) Pb (L. plumbum); at. wt. 207.2; at. no.82; m.p. 327.5020C; b.p. 17400C; sp. gn 11.35 (200C); valence 2 or 4. Long known; mentioned in Exodus. The alchemists believed lead to be the oldest metal and associated it with the planet Saturn. Native lead occurs in nature, but it is rare. Lead is obtained chiefly from galena (PbS) by a roasting process. Anglesite (PbSO4), Cerrusite (PbCO3), and Minim (Pb3O4) are other common lead minerals. Lead is a bluish-white metal of bright luster, very soft, highly malleable, is ductile and a poor conductor of electricity. It is very resistant to corrosion; lead pipes bearing the insignia of Roman emperors, used as drains from the baths, are still in service. It is used as containers for cor- rosive liquids, such as in sulfuric acid chambers, and it may be toughened by the addition of a small percentage of antimony or other metals. Natural lead is a mixture of four stable isotopes: Pb204 (1.48%), Pb206 (23.6%), Pb207 (22.6%), and Pb208 (52.3%). Lead isotopes are the end pro- ducts of each of the three series of naturally occurring radio- active elements: Pb206 for the uranium series, Pb207 for the actinium series, and Pb208 for the thorium series. Twenty-five other isotopes of lead, all of which are radioactive, are recog- nized. Its alloys include solder, type metal, and various anti- friction metals. Great quantities of lead, both as the metal and as the dioxide, are used in storage batteries. Much metal also goes into cable covering, plumbing, ammunition, and in the manufacture of lead tetraethyl, used as an anti-knock com- pound in gasoline. The metal is very effective as a sound absorber, is used as a radiation shield around x-ray equip- ment and nuclear reactors, and is used to absorb vibration. White lead, the basic lead carbonate, sublimed white lead (PbSO4), chrome yellow (PbCrO4), red lead (Pb3O4) and other lead compounds are extensively used in paints. Lead oxide is used in producing fine "crystal glass" and "flint glass" of a high index of refraction for achromatic lenses. The nitrate and the acetate are soluble salts. Lead salts such THE ELEMENT~CDntiflue) as lead arsenate, have been used as insecticides, but their use in recent years has been practically eliminated and replaced with less harmful organic compounds. Care must be used in handling lead as it is a cumulative poison.

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