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Elements Hydrogen Number of: Protons 1 Neutrons 0 Electrons 1 Boiling point -252 Freezing point -259 State at room temperature gas Brief description: hydrogen is the lightest element. It is by far the most abundant element in the universe and makes up about about 90% of the universe by weight. Hydrogen as water (H2O) is absolutely essential to life and it is present in all organic compounds. Hydrogen is the lightest gas. Hydrogen gas was used in lighterthan-air balloons for transport but is far too dangerous because of the fire risk (Hindenburg). It burns in air to form only water as waste product and if hydrogen could be made on sufficient scale from other than fossil fuels then there might be a possibility of a hydrogen economy. Elements Helium Number of: Protons 2 Neutrons 2 Electrons 2 Boiling point -268 Freezing point -272 State at room temperature gas Brief description: helium is one of the so-called noble gases. Helium gas is an unreactive, colourless, and odourless gas. Helium is available in pressurised tanks. Helium is the second most abundant element in the universe after hydrogen. Helium is used in lighter than air balloons and while heavier than hydrogen, is far safer since helium does not burn. Speaking after breathing an atmosphere rich in helium results in a squeaky Elements Lithium Number of: Protons 3 Neutrons 4 Electrons 3 Boiling point 1347 Freezing point 180 State at room temperature solid Brief description: lithium is a Group 1 element Group 1 elements are called "alkali metals". Lithium is a solid only about half as dense as water and lithium metal is the least dense metal. A freshly cut chunk of lithium is silvery, but tarnishes in a minute or so in air to give a grey surface. Lithium is mixed (alloyed) with aluminium and magnesium for light-weight alloys, and is also used in batteries, some greases, some glasses, and in medicine. Elements Boron Number of: Protons 5 Neutrons 5 Electrons 5 Boiling point 2550 Freezing point 2300 State at room temperature solid Brief description: boron is a Group 13 element that has properties which are borderline between metals and non-metals (semi metallic). It is a semiconductor rather than a metallic conductor. Chemically it is closer to silicon than to aluminium, gallium, indium, and thallium. Elements Carbon Number of: Protons 6 Neutrons 6 Electrons 6 Boiling point 3440 Freezing point 4827 State at room temperature solid Brief description: carbon is a Group 14 element and is distributed very widely in nature. It is found in abundance in the sun, stars, comets, and atmospheres of most planets. Carbon is found free in nature in three allotropic forms: amorphous, graphite, and diamond. Graphite is one of the softest known materials while diamond is one of the hardest. Carbon, as microscopic diamonds, is found in some meteorites. Natural diamonds are found in ancient volcanic "pipes" such as found in South Africa. Diamonds are also recovered from the ocean floor off the Cape of Good Hope. Elements Oxygen Number of: Protons 8 Neutrons 8 Electrons 8 Boiling point -182 Freezing point - 218 State at room temperature gas Brief description: oxygen is a Group 16 element. While about one fifth of the atmosphere is oxygen gas, the atmosphere of Mars contains only about 0.15% oxygen. Oxygen is the third most abundant element found in the sun, and it plays a part in the carbon-nitrogen cycle, one process responsible for stellar energy production. About two thirds of the human body, and nine tenths of water, is oxygen. The gas is colourless, odourless, and tasteless. Liquid and solid oxygen are pale blue. Elements Fluorine Number of: Protons 9 Neutrons 10 Electrons 9 Boiling point -188 Freezing point - 219 State at room temperature gas Brief description: fluorine is a Group 17 element. Fluorine is the most electronegative and reactive of all elements. It is a pale yellow, corrosive gas, which reacts with practically all organic and inorganic substances. Finely divided metals, glass, ceramics, carbon, and even water burn in fluorine with a bright flame. It is not uncommon to see fluorine spelled incorrectly as flourine. Elements Sodium Number of: Protons 11 Neutrons 12 Electrons 11 Boiling point Freezing point 882 97 State at room temperature solid Brief description: sodium is a Group 1 element which are often referred to as the "alkali metals". Sodium salts impart a characteristic orange/yellow colour to flames and orange street lighting is orange because of the presence of sodium in the lamp. Soap is generally a sodium salt of fatty acids. The importance of common salt to animal nutrition has been recognized since prehistoric times. The most common compound is sodium chloride, (table salt). Elements Magnesium Number of: Protons 12 Neutrons 12 Electrons 12 Boiling point 1090 Freezing point 648 State at room temperature solid Brief description: magnesium is a greyish-white, fairly tough metal. Magnesium is the eighth most abundant element in the earth's crust although not found in it's elemental form. It is a Group 2 element Group 2 elements are called alkaline earth metals. Magnesium metal burns with a very bright light. Magnesium is an important element for plant and animal life. The adult human daily requirement of magnesium is about 0.3 g day-1 Elements Potassium Number of: Protons 19 Neutrons 20 Electrons 19 Boiling point 774 Freezing point 63 State at room temperature solid Brief description: potassium is a metal and is the seventh most abundant and makes up about 1.5 % by weight of the earth's crust. Potassium is an essential constituent for plant growth and it is found in most soils. It is also a vital element in the human diet. Potassium is never found free in nature, but is obtained by electrolysis of the chloride or hydroxide. It is one of the most reactive and electropositive of metals and, apart from lithium, it is the least dense known metal. It is soft and easily cut with a knife. It is silvery in appearance immediately after a fresh surface is exposed. Elements Calcium Number of: Protons 20 Neutrons 20 Electrons 20 Boiling point 1484 Freezing point 839 State at room temperature solid Brief description: calcium as the element is a grey silvery metal. The metal is rather hard. Calcium is an essential constituent of leaves, bones, teeth, and shells. Calcium is the fifth most abundant element in the earth's crust and makes up more than 3% of the crust. Calcium does not occur as the metal itself in nature and instead is found in various minerals including as limestone, gypsum and fluorite. Stalagmites and stalactites contain calcium carbonate (CaCO3). Calcium carbonate is the basis of the cement industry. Elements Iron Number of: Protons 26 Neutrons 30 Electrons 26 Boiling point 2750 Freezing point 1535 State at room temperature solid Brief description: Iron is a relatively abundant element in the universe. It is found in the sun and many types of stars in considerable quantity. Iron nuclei are very stable. Iron is a vital constituent of plant and animal life, and is the key component of haemoglobin. The pure metal is not often encountered in commerce, but is usually alloyed with carbon or other metals. The pure metal is very reactive chemically, and rapidly corrodes, especially in moist air or at elevated temperatures. Any car owner knows this. Iron metal is a silvery, lustrous metal which has important magnetic properties. Elements Copper Number of: Protons 29 Neutrons 35 Electrons 29 Boiling point 2567 Freezing point 1083 State at room temperature solid Brief description: Copper is one of the most important metals. Copper is reddish with a bright metallic lustre. It is malleable, ductile, and a good conductor of heat and electricity (second only to silver in electrical conductivity). Its alloys, brass and bronze, are very important. Gun metals also contain copper. Apparently the reason that policemen in the USA are nicknamed “cop" or “copper" is to do with their uniforms which used to have copper buttons. Elements Zinc Number of: Protons 30 Neutrons 35 Electrons 30 Boiling point 907 Freezing point 419 State at room temperature solid Brief description: Zinc-deficient animals require 50% more food to gain the same weight of an animal supplied with adequate amounts of zinc. Zinc is not particularly toxic and is an essential element in the growth of all animals and plants. Plating thin layers of zinc on to iron or steel is known as galvanising and helps to protect the iron from corrosion. Elements Nitrogen Number of: Protons 7 Neutrons 7 Electrons 7 Boiling point -209 Freezing point -195 State at room temperature gas Brief description: Nitrogen is a Group 15 element. Nitrogen makes up about 78% of the atmosphere by volume but the atmosphere of Mars contains less than 3% nitrogen. The element seemed so inert that Lavoisier named it azote, meaning "without life". However, its compounds are vital components of foods, fertilizers, and explosives. Nitrogen gas is colourless, odourless, and generally inert. As a liquid it is also colourless and odourless. Elements Aluminium Number of: Protons 13 Neutrons 14 Electrons 13 Boiling point 2467 Freezing point 660 State at room temperature solid Brief description: pure aluminium is a silvery-white metal with many desirable characteristics. It is light, nontoxic (as the metal), nonmagnetic and nonsparking. It is somewhat decorative. It is easily formed, machined, and cast. Pure aluminium is soft and lacks strength, but alloys with small amounts of copper, magnesium, silicon, manganese, and other elements have very useful properties. Aluminium is an abundant element in the earth's crust, but it is not found free in nature. Elements Silicon Number of: Protons 14 Neutrons 14 Electrons 14 Boiling point 2355 Freezing point 1410 State at room temperature solid Brief description: silicon is present in the sun and stars and is a principal component of a class of meteorites known as aerolites. Silicon makes up 25.7% of the earth's crust by weight, and is the second most abundant element, exceeded only by oxygen. It is found largely as silicon oxides such as sand (silica), quartz, rock crystal, amethyst, agate, flint, jasper and opal. Silicon is found also in minerals such as asbestos, feldspar, clay and mica. Elements Phosphorus Number of: Protons 15 Neutrons 16 Electrons 15 Boiling point 280 Freezing point 44 State at room temperature solid Brief description: It is an essential component of living systems and is found in nervous tissue, bones and cell protoplasm. Phosphorus exists in several forms including white (or yellow), red, and black (or violet). White phosphorus has two modifications. Ordinary phosphorus is a waxy white solid. When pure, it is colourless and transparent. It is insoluble in water. It catches fire spontaneously in air. Elements Sulphur Number of: Protons 16 Neutrons 16 Electrons 16 Boiling point 444 Freezing point 112 State at room temperature solid Sulphur is found in meteorites, volcanoes, hot springs, and as galena, gypsum, Epsom salts, and barite. It is recovered commercially from "salt domes" along the Gulf Coast of the USA. Jupiter's moon Io owes its colours to various forms of sulphur. A dark area near the crater Aristarchus on the moon may be a sulphur deposit. Sulphur is a pale yellow, odourless, brittle solid, which is insoluble in water. Sulphur is essential to life. It is a minor constituent of fats, body fluids, and skeletal minerals. Elements Silver Number of: Protons 47 Neutrons 61 Electrons 47 Boiling point Freezing point 2212 961 State at room temperature solid Brief description: Silver is somewhat rare and expensive, although not as expensive as gold. Pure silver has a brilliant white metallic lustre. It is a little harder than gold and is very ductile and malleable. Pure silver has the highest electrical and thermal conductivity of all metals, and possesses the lowest contact resistance. Elements Gold Number of: Protons 79 Neutrons 118 Electrons 79 Boiling point 2807 Freezing point 1064 State at room temperature solid Brief description: gold is usually alloyed in jewellery to give it more strength, and the term carat describes the amount of gold present (24 carats is pure gold). It is estimated that all the gold in the world, so far refined, could be placed in a single cube 60 ft. on a side. It is metallic, with a yellow colour when in a mass, but when finely divided it may be black, ruby, or purple. Elements Uranium Number of: Protons 92 Neutrons 141-146 Electrons 92 Boiling point 3818 Freezing point 1132 State at room temperature solid Brief description: uranium is of great interest because of its application to nuclear power and nuclear weapons. Uranium contamination is an emotive environmental problem. It is not particularly rare and is more common than beryllium or tungsten for instance