Ytterbium has a bright silvery luster, is soft, malleable, and quite ductile. Wliile the elemetit is fairly stable, it should be kept in closed containers td protect it from air and moisture. Ytterbium is readily attacked and dissolved by dilute and concentrated mineral acids and reacts slowly with water. Another body-centered cubic phase has recently been found to be stable at high pressures at room temperatures. The alpha form ordinarily has metallic-type conductivity, but becomes a semiconductor when the pressure is increased above 16,000 atm.
Natural ytterbium is a mixture of seven stable isotopes.
Nine other unstable isotopes are known. One isotope is reported to have been used as a radiation source as a substitute for a portable x-ray machine where electricity is unavailable. Few other uses have been found. Yrterbium has a low acute toxic rating.