Arsenic, antimony, bismuth element and hydride

12.
5.
1 Simple substance

Arsenic, antimony, and bismuth have many allotropes
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The most stable arsenic at room temperature is metallic gray arsenic (a-As), which has a corrugated layered structure

Room temperature arsenic, antimony and bismuth are relatively stable in water and air, does not effect a non-oxidizing dilute acid, and nitric acid, but it can, aqua regia and other reactions
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When nitric acid is not excessive , arsenic and sharp are oxidized to +3 valent compounds, and when nitric acid is excessive, they are oxidized to +5 valent compounds; while bismuth and nitric acid can only generate +3 valent compounds

12.
5.

AsH ₃ , SbH ₃ , and BiH ₃ are all gases at room temperature, and their melting and boiling points increase in sequence, but their stability decreases in sequence
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AsH ₃ can be obtained by reducing the oxide of arsenic with a strong reducing agent
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As ₂ O ₃ +6Zn+12HCl=2AsH ₃ +6ZnCl ₂ +3H ₂ O

The generated gas is introduced into the glass tube and heated, and AsH3 is decomposed into elemental As by heating
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2AsH ₃ =2As+3H ₂

The elemental As forms a black and bright "arsenic mirror" on the wall of the glass tube
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This reaction is the basis of the Marsh test method for arsenic identification in forensic medicine

A similar method can be used to generate SbH ₃ gas.
SbH _{3 is} unstable and decomposes at room temperature to obtain "Jin Jing"
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The hydrides of arsenic, antimony, and bismuth are all strong reducing agents and can ignite spontaneously in the air
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2AsH ₃ +3O ₂ =As ₂ O ₃ +3H ₂ O

AsH ₃ can reduce heavy metal salts to obtain heavy metal elements
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The Gutzeit arsenic test method is a reaction of using AsH _{2 to} reduce silver nitrate to produce Ag precipitation

2AsH ₃ +12AgNO ₃ +3H ₂ O=A ₂ O ₃ +12HNO ₃ +12Ag↓