Page 52 - The Periodic Table Book
P. 52
88
Ra Radium
State: Solid
88 88 138 Discovery: 1898
Alkaline Earth Metals Chunk of uraninite This ore contains just 0.7 g In 100
Forms
(0.02 oz) of radium in every
1,000 kg (2,205 lb) of rock.
years time,
only 4% of the
radium atoms in this
watch would have
broken down.
Radium is the only radioactive member with most of them quickly decaying into
of the alkaline earth metals. It is also the radon, a radioactive noble gas. This element
rarest element in this group, and forms in small is highly dangerous and is rarely used today.
amounts when the atoms of more common However, in the early 20th century, radium
metals – such as uranium and thorium – break compounds were in common use. Luminous
50 down. Radium atoms do not survive for long, paints, like those used to make watch dials
050-051_Radium.indd 50 02/12/16 6:52 pm
