Please answer the following question: Information: - An ion is an atom or a molecule in which the total number of electrons is not equal to the total number of protons, giving the atom or molecule a net positive or negative electrical charge. Ions can be created, by either chemical or physical means, via ionization. - In mineralogy, argentite (from the Latin "argentum", silver) is cubic silver sulfide (AgS), which can only exist at temperatures above 173C, 177C or 179C. When it cools to ordinary temperatures it turns into its monoclinic polymorph, acanthite. Argentite belongs to the galena group. - In physics, thermal conductivity (often denoted "k", "", or "") is the property of a material to conduct heat. It is evaluated primarily in terms of Fourier's Law for heat conduction. - Silver sulfide ( Ag - Latin (Latin: ) is a classical language belonging to the Italic branch of the Indo-European languages. The Latin alphabet is derived from the Etruscan and Greek alphabets. - A per mille (from Latin " mlle", "in each thousand"), also spelled per mil, per mill, permil, permill, or permille is a sign indicating parts per thousand. Per mil should not be confused with parts per million (ppm). - Silver is the metallic element with the atomic number 47. Its symbol is Ag, from the Latin "", derived from the Greek "" (literally "shiny" or "white"), and ultimately from a Proto-Indo-European language root reconstructed as *"her-", "grey" or "shining". A soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. The metal is found in the Earth's crust in the pure, free elemental form ("native silver"), as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. Most silver is produced as a byproduct of copper, gold, lead, and zinc refining. Silver is more abundant than gold, but it is much less abundant as a native metal. Its purity is typically measured on a per mille basis; a 94%-pure alloy is described as "0.940 fine". - Lead, from the Old English "lead", is a chemical element with atomic number82 and symbolPb (after the Latin, "plumbum"). It has the second highest atomic number of all practically stable elements. As such, lead is located at the end of some decay chains of heavier elements, which in part accounts for its relative abundance: its stability exceeds those of other similarly-numbered elements. Lead is a soft, malleable, and heavy metal. Freshly cut lead has a bluish-white color that soon tarnishes to a dull grayish color when exposed to air; as a liquid, it has a shiny chrome-silver luster. Lead's density of 11.34g/cm exceeds those of most common materials. - A native metal is any metal that is found in its metallic form, either pure or as an alloy, in nature. Metals that can be found as native deposits singly or in alloys include aluminium, antimony, arsenic, bismuth, cadmium, chromium, cobalt, indium, iron, manganese, molybdenum, nickel, rhenium, selenium, tantalum, tellurium, tin, titanium, tungsten, vanadium, and zinc, as well as two groups of metals: the gold group, and the platinum group. The gold group consists of gold, copper, lead, aluminium, mercury, and silver. The platinum group consists of platinum, iridium, osmium, palladium, rhodium, and ruthenium. Amongst the alloys found in native state have been brass, bronze, pewter, German silver, osmiridium, electrum, white gold, and silver-mercury and gold-mercury amalgam. - Zinc is a chemical element with the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. In some respects zinc is chemically similar to magnesium: both elements exhibit only one normal oxidation state (+2), and the Zn and Mg ions are of similar size. Zinc is the 24th most abundant element in Earth's crust and has five stable isotopes. The most common zinc ore is sphalerite (zinc blende), a zinc sulfide mineral. The largest workable lodes are in Australia, Asia, and the United States. Zinc is refined by froth flotation of the ore, roasting, and final extraction using electricity (electrowinning). - Proto-Indo-European (PIE) is the linguistic reconstruction of the common ancestor of the Indo-European languages, the most widely spoken language family in the world. Far more work has gone into reconstructing PIE than any other proto-language, and it is by far the best understood of all proto-languages of its age. The vast majority of linguistic work during the 19th century was devoted to reconstruction of PIE or its daughter proto-languages (e.g. Proto-Germanic), and most of the modern techniques of linguistic reconstruction such as the comparative method were developed as a result. These methods supply all of the knowledge concerning PIE, since there is no written record of the language. - Tin is a chemical element with the symbolSn (for ) and atomic number50, is a post-transition metal in group 14 of the periodic table. It is obtained chiefly from the mineral cassiterite, which contains tin dioxide, SnO. Tin shows a chemical similarity to both of its neighbors in group 14, germanium and lead, and has two main oxidation states, +2 and the slightly more stable +4. Tin is the 49th most abundant element and has, with 10 stable isotopes, the largest number of stable isotopes in the periodic table, thanks to its magic number of protons. It has two main allotropes: at room temperature, the stable allotrope is -tin, a silvery-white, malleable metal, but at low temperatures it transforms into the less dense grey -tin, which has the diamond cubic structure. Metallic tin is not easily oxidized in air. - Gold is a chemical element with the symbol Au (from ) and the atomic number 79. In its purest form, it is a bright, slightly reddish yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal and a group 11 element. It is one of the least reactive chemical elements and is solid under standard conditions. Gold often occurs in free elemental (native) form, as nuggets or grains, in rocks, in veins, and in alluvial deposits. It occurs in a solid solution series with the native element silver (as electrum) and also naturally alloyed with copper and palladium. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides). - Sulfide (systematically named sulfanediide, and sulfide(2)) is an inorganic anion of sulfur with the chemical formula S. It contributes no color to sulfide salts. As it is classified as a strong base, even dilute solutions of salts such as sodium sulfide (NaS) are corrosive and can attack the skin. Sulfide is the simplest sulfur anion. - Refining (also perhaps called by the mathematical term affining) is the process of purification of a (1) substance or a (2) form. The term is usually used of a natural resource that is almost in a usable form, but which is more useful in its pure form. For instance, most types of natural petroleum will burn straight from the ground, but it will burn poorly and quickly clog an engine with residues and by-products. The term is broad, and may include more drastic transformations, such as the reduction of ore to metal (for which see Refining (metallurgy)). - Sodium sulfide is the chemical compound with the formula NaS, or more commonly its hydrate NaS9HO. Both are colorless water-soluble salts that give strongly alkaline solutions. When exposed to moist air, NaS and its hydrates emit hydrogen sulfide, which smells like rotten eggs. Some commercial samples are specified as NaS"x"HO, where a weight percentage of NaS is specified. Commonly available grades have around 60% NaS by weight, which means that "x" is around 3. Such technical grades of sodium sulfide have a yellow appearance owing to the presence of polysulfides. These grades of sodium sulfide are marketed as 'sodium sulfide flakes'. Although the solid is yellow, solutions of it are colorless. - An alloy is a mixture of metals or a mixture of a metal and another element. Alloys are defined by a metallic bonding character. An alloy may be a solid solution of metal elements (a single phase) or a mixture of metallic phases (two or more solutions). Intermetallic compounds are alloys with a defined stoichiometry and crystal structure. Zintl phases are also sometimes considered alloys depending on bond types (see also: Van Arkel-Ketelaar triangle for information on classifying bonding in binary compounds). - In chemistry and physics, the atomic number of a chemical element (also known as its proton number) is the number of protons found in the nucleus of an atom of that element, and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element. In an uncharged atom, the atomic number is also equal to the number of electrons. - A metal (from Greek "metallon", "mine, quarry, metal") is a material (an element, compound, or alloy) that is typically hard, opaque, shiny, and has good electrical and thermal conductivity. Metals are generally malleable that is, they can be hammered or pressed permanently out of shape without breaking or cracking as well as fusible (able to be fused or melted) and ductile (able to be drawn out into a thin wire). About 91 of the 118 elements in the periodic table are metals, the others are nonmetals or metalloids. Some elements appear in both metallic and non-metallic forms. - Sulfur or sulphur (see spelling and etymology) is a chemical element with symbolS and atomic number16. It is abundant, multivalent, and nonmetalic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S. Elemental sulfur is a bright yellow crystalline solid at room temperature. Chemically, sulfur reacts with all elements except for gold, platinum, iridium, tellurium, and the noble gases. - Copper is a chemical element with symbol Cu (from ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a reddish-orange color. Copper is used as a conductor of heat and electricity, as a building material, and as a constituent of various metal alloys, such as sterling silver used in jewelry, cupronickel used to make marine hardware and coins, and constantan used in strain gauges and thermocouples for temperature measurement. - In chemistry, the term transition metal (or transition element) has three possible meanings: - Chlorargyrite is the mineral form of silver chloride (AgCl). Chlorargyrite occurs as a secondary mineral phase in the oxidation of silver mineral deposits. It crystallizes in the isometric - hexoctahedral crystal class. Typically massive to columnar in occurrence it also has been found as colorless to variably yellow cubic crystals. The color changes to brown or purple on exposure to light. It is quite soft with a Mohs hardness of 1 to 2 and dense with a specific gravity of 5.55. It is also known as cerargyrite and, when weathered by desert air, as horn silver. Bromian chlorargyrite (or embolite) is also common. Chlorargyrite is water-insoluble. After reading the paragraphs above, we are interested in knowing the entity with which 'silver sulfide' exhibits the relationship of 'instance of'. Find the answer from the choices below. Choices: - 1 - 12 - age - alloy - alphabet - anion - branch - building - chemical - chemical compound - chemical element - chloride - cut - desert - extraction - final - fine - formula - good - group - information - intermetallic - ion - language - language family - law - liquid - may - metal - mill - mine - mineral - molecule - natural resource - nucleus - number - ordinary - ore - part - phase - physics - pie - process - property - result - room - shape - sign - size - solution - stable - standard - strain - surface - symbol - temperature - term - three - two - water - wire
A:
chemical compound