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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

FRANCIUM (France), Fr; at. no.87; at. wt. 223 (most stable 'isotope); valence 1. Discovered in 1939 by MIle, Marguerite Perey of the Curie Institute, Paris. Francium, the heaviest known member of the alkali metal series, occurs as-a result of an alpha disintegration of actinium. It can also be made- artificially by bombarding thorium with protons. While it occurs naturally in uranium minerals, there is probably less than an ounce of francium at any time in the total crust of the earth. It has the highest equivalent weight of any element, and is the most unstable of the first 101 elements of the periodic system. Twenty-one isotopes of francium are recognized. The longest lived, Fr223(AcK) a daughterofAc227, hasahalf-lifeof22minutes.Thisis the only isotope of francium occurring in nature. Because all known isotopes of francium are highiy unstable, knowledge of the chemical properties ofthis elementcomes from radiochemical techniques. No weighable quantity of the element has been ITIE ELEMEN.W4Contiiiued) prepared or isolated. The chemical properties of francium most closely resemble cesium.

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