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Gray, or metallic arsenic, pictured under an argon atmosphere. Gray arsenic, also called grey arsenic or metallic arsenic, is the most stable allotrope of the element at room temperature, and as such is its most common form. [1] This soft, brittle allotrope of arsenic has a steel gray, metallic color, and is a good conductor. [2]
This compound is generally regarded as stable, since at room temperature it decomposes only slowly. At temperatures of 250–300 °C decomposition to arsenic and hydrogen is rapid. [34] Several factors, such as humidity, presence of light and certain catalysts (namely aluminium) facilitate the rate of decomposition. [35]
One of the simplest arsenic compound is the trihydride, the highly toxic, flammable, pyrophoric arsine (AsH 3). This compound is generally regarded as stable, since at room temperature it decomposes only slowly. At temperatures of 250–300 °C decomposition to arsenic and hydrogen is rapid. [3]
Most alloys of arsenic with metals lack metallic or semimetallic conductivity. The common oxide of arsenic (As 2 O 3) is acidic but weakly amphoteric. Antimony, showing its brilliant lustre. Antimony is a silver-white solid with a blue tint and a brilliant lustre. It is stable in air and moisture at room temperature.
In its standard state arsine is a colorless, denser-than-air gas that is slightly soluble in water (2% at 20 °C) [1] and in many organic solvents as well. [citation needed] Arsine itself is odorless, [5] but it oxidizes in air and this creates a slight garlic or fish-like scent when the compound is present above 0.5 ppm. [6]
33 As arsenic; use (T/K) 553 596 646 706 781 874 CRC.c (T/°C ... Indicates the substance is solid at this temperature. As quoted from these sources: a - Lide, D ...
For gases, departure from 3 R per mole of atoms is generally due to two factors: (1) failure of the higher quantum-energy-spaced vibration modes in gas molecules to be excited at room temperature, and (2) loss of potential energy degree of freedom for small gas molecules, simply because most of their atoms are not bonded maximally in space to ...
Similarly, yellow arsenic is a molecular solid composed of As 4 units. [37] Some forms of sulfur and selenium are composed of S 8 (or Se 8 ) units and are molecular solids at ambient conditions, but converted into covalent allotropes having atomic chains extending throughout the crystal.