Bismuth is a brittle, crystalline, silvery-pink post-transition metal. It is strongly diamagnetic, expands on solidification, and is far less toxic than lead, so it is used in low-toxicity alloys, pharmaceuticals, pigments, and cosmetics.
The electron configuration of bismuth is [Xe] 4f14 5d10 6s2 6p3. It has five valence electrons, similar to other group 15 elements like nitrogen and arsenic, allowing oxidation states of +3 and +5.
In bismuth, the inert pair effect causes the 6s electrons to remain non-bonding due to relativistic stabilization and poor shielding by inner d and f orbitals. This makes the +3 oxidation state (Bi3+) more stable than the +5 state (Bi5+).
\(\mathrm{Bi^{5+} \rightarrow Bi^{3+} + 2e^-}\)
Bismuth exhibits oxidation states of +3 and +5. The +3 state is more stable, found in compounds like BiCl3 and Bi2O3, while the +5 state appears in strong oxidizing conditions, as in BiF5.
Bismuth is far less toxic than lead because it is poorly absorbed by the human body and does not interfere with biological enzymes to the same extent. This property allows its safe use in medicines such as bismuth subsalicylate (Pepto-Bismol) for treating stomach ailments.
Bismuth has a variety of applications, including:
Bismuth is a brittle, silvery-pink metal that has low thermal conductivity and expands on solidification—unlike most metals. It has a melting point of 271.4 °C and a boiling point of 1564 °C. It is also strongly diamagnetic.
Common compounds of bismuth include:
Bismuth is relatively inert and forms a thin oxide layer when exposed to air:
\(\mathrm{4\,Bi + 3\,O_2 \rightarrow 2\,Bi_2O_3}\)
It dissolves slowly in concentrated nitric acid forming bismuth nitrate:
\(\mathrm{Bi + 6\,HNO_3 \rightarrow Bi(NO_3)_3 + 3\,NO_2 + 3\,H_2O}\)
Bismuth expands upon solidification because its solid crystalline structure is less dense than the liquid form. This unique property is shared with water and is useful in casting processes where expansion prevents shrinkage defects.
Bismuth is strongly diamagnetic due to its paired electrons and filled electronic subshells. It generates an induced magnetic field opposite to an external magnetic field, causing it to be repelled by magnets.
Bismuth occurs both in native metallic form and in ores such as bismuthinite (Bi2S3) and bismite (Bi2O3). It is primarily obtained as a by-product of refining lead, copper, tin, and silver ores.