Carbon forms strong, stable covalent bonds to other carbon atoms, and is capable of forming long chains containing anywhere from a few dozen carbon atoms to hundred of thousands of carbon atoms. Carbon can also form bonds to other elements, such as hydrogen, oxygen, nitrogen, sulfur, phosphorus, the halogens, etc.
There are therefore a tremendous variety of complex carbon-based chemicals. Organic chemistry is the field of chemistry concerned with the study of carbon-containing compounds. Such compounds form the basis of life at least the kinds that we know about. Carbon is found is coal, and petroleum is a very complex mixture of thousands of different hydrocarbons. The burning of carbon and petroleum products fossil fuels provides most of the energy which we consume, and contributes to global warming through the release of carbon dioxide into the atmosphere.
Carbon is used is the refining of iron and other metals the oxygen in the ores is carried away in the form of carbon dioxide, leaving behind the elemental metal. Small amounts of carbon are added to iron to make an alloy called steel, which is harder than pure iron. Activated charcoal is a finely powdered form of carbon used to filter out impurities from water or gases.
Carbon is taken up by green plants in the form of carbon dioxide, CO 2 ; in the process of photosynthesis, the carbon in the carbon dioxide is transformed into carbohydrates sugars , lipids, proteins, and all of the other organic molecules which are essential to life. Most carbon is in the form of the carbon isotope Carbon, which is also non-radioactive, accounts for 1. Carbon is particularly important in nuclear magnetic resonance spectroscopy see the section on Hydrogen ; organic molecules contain small amounts of carbon, which responds to magnetic fields in a similar fashion as hydrogen Carbon, which consists of 6 protons and 8 neutrons, is an unstable isotope produced the reaction of free neutrons produced from cosmic rays with nitrogen in the upper atmosphere.
Carbon undergoes beta decay to produce nitrogen, with a half-life of years:. The amount of carbon thus produced is extremely small — approximately 7 kilograms per year — but small amounts of this carbon are taken up in the form of carbon dioxide along with the "normal" isotopes of carbon by green plants, and this isotope also becomes incorporated into the things that eat the green plants and also the things that eat the things that eat the green plants — and so on.
Once an organism dies, it stops taking in carbon or anything else, for that matter , and the carbon that it had at the moment of death decays, and is no longer replaced. By measuring the amount of carbon remaining in an organic sample, it is possible to determine how long ago the organism died. This technique works for carbon-containing materials that are up to about 50, years old; beyond that, there is too little carbon remaining to get an accurate date, and some other form of radiometric dating must be used.
This technique was developed by Willard F. Libby in the s, who received the Nobel Prize in Chemistry in for this work. Silicon is a dark gray element with a metallic luster. The name of the element is derived from the Latin word for flint, silicis. In the form of silica SiO 2 or one of the silicates SiO 4 4- , it is found in many different minerals, including clay, quartz, zircon, feldspar, mica, zeolites, aluminosilicates, sand, etc. It is also found in the gemstones opal, agate, rhinestone, and amethyst.
Silicon is one of the most important elements on the periodic table at least from the perspective of computers! Ultrapure silicon doped with boron or phosphorus is used as semiconductors in transistors, which are heavily employed in computers, solar panels, and other applications. Therefore, sodium tends to lose an electron to become more stable.
On the other hand, chlorine tends to gain an electron to become Cl —. Chlorine naturally has 17 electrons but it would be more stable with 18 electrons 2 in its inner most shell, 8 in its second shell, and 8 in its valence shell. Therefore, chlorine will take an electron from another atom to become negatively charged. Periodic Properties: Part 3, Ionic Radius, Predicting Ionic Charges — YouTube : A continuation of the discussion of periodic properties, including ionic radius and how to predict ionic charges.
Privacy Policy. Skip to main content. Atoms, Molecules, and Ions. Search for:. The Periodic Table The Periodic Table The periodic table shows all the elements and their physical properties; it is arranged based on atomic numbers and electron configurations.
Learning Objectives Identify the common periodic trends that can be deduced from the periodic table of elements. Key Takeaways Key Points The periodic table lists all the elements, with information about their atomic weights, chemical symbols, and atomic numbers. The arrangement of the periodic table leads us to visualize certain trends among the atoms. The vertical columns groups of the periodic table are arranged such that all its elements have the same number of valence electrons.
All elements within a certain group thus share similar properties. Key Terms atomic number : The number, equal to the number of protons in an atom, that determines its chemical properties. Molecules Molecules are electrically neutral compounds made of multiple atoms bound together by chemical bonds. Learning Objectives Recognize the general properties of molecules. Key Takeaways Key Points Molecules are neutral and do not carry any charge. A molecule may consist of nonmetallic atoms of a single chemical element, as with oxygen O 2 , or of different elements, as with water H 2 O.
The geometry and composition of a molecule will determine its chemical and physical properties. Key Terms covalent : when 2 or more nonmetallic atoms are bound together by sharing electrons. All compounds are molecules but not all molecules are compounds. Ions An ion is an atom or molecule that has a net electrical charge because its total number of electrons is not equal to its number of protons.
Learning Objectives Compare the different classes of ions. Key Takeaways Key Points Ions are formed when the number of protons in an atom does not equal the number of electrons. If more protons are present, the ion is positive and is known as a cation; if more electrons are present, the ion is negative and referred to as an anion. Key Terms ion : An atom or group of atoms bearing an electrical charge, such as the sodium and chlorine atoms in a salt solution.
Licenses and Attributions. The chemical elements are divided into the metals, the metalloids, and the non-metals.
Metals, typically found on the left side of the periodic table, are:. In contrast, non-metals, found on the right side of the periodic table to the right of the staircase , are:. Metalloids have some characteristics of metals and some characteristics of non-metals. Silicon and arsenic are metalloids.
As of November, , elements have been identified the most recently identified was ununseptium, in Of these known elements, only the first 98 are known to occur naturally on Earth.
The elements that do not occur naturally on Earth are the synthetic products of man-made nuclear reactions. The periodic table : The periodic table shows elements, including metals blue , nonmetals red , and metalloids green. Hydrogen and helium are by far the most abundant elements in the universe.
The remainder is dark matter, a mysterious substance that is not composed of chemical elements. Dark matter lacks protons, neutrons, or electrons. Pure samples of isolated elements are uncommon in nature. Carbon is also commonly found in the form of coal, graphite, and diamonds. The noble gases e. Still, most of these elements are found in mixtures. When two distinct elements are chemically combined—i. Most elements on Earth bond with other elements to form chemical compounds, such as sodium Na and Chloride Cl , which combine to form table salt NaCl.
Water is another example of a chemical compound. The two or more component elements of a compound can be separated through chemical reactions. Chemical compounds have a unique and defined structure, which consists of a fixed ratio of atoms held together in a defined spatial arrangement by chemical bonds. Chemical compounds can be:. Pure chemical elements are not considered chemical compounds, even if they consist of diatomic or polyatomic molecules molecules that contain only multiple atoms of a single element, such as H 2 or S 8.
Privacy Policy. Skip to main content. Introduction to Chemistry. Search for:. Classification of Matter Three States of Matter The three states of matter are the distinct physical forms that matter can take: solid, liquid, and gas. Learning Objectives Describe the three states of matter.
Key Takeaways Key Points Matter can exist in one of three main states: solid, liquid, or gas. Solid matter is composed of tightly packed particles. A solid will retain its shape; the particles are not free to move around. Liquid matter is made of more loosely packed particles.
It will take the shape of its container. Particles can move about within a liquid, but they are packed densely enough that volume is maintained. Gaseous matter is composed of particles packed so loosely that it has neither a defined shape nor a defined volume.
A gas can be compressed. Key Terms liquid : A substance that flows and keeps no definite shape because its molecules are loosely packed and constantly moving. It takes the shape of its container but maintains constant volume.
Substances and Mixtures Substances are composed of pure elements or chemically bonded elements, whereas mixtures are composed of non-bonded substances. Learning Objectives Distinguish chemical substances from mixtures. Key Takeaways Key Points Matter can be broken down into two categories: pure substances and mixtures. Pure substances are further broken down into elements and compounds. Mixtures are physically combined structures that can be separated into their original components. A chemical substance is composed of one type of atom or molecule.
A mixture is composed of different types of atoms or molecules that are not chemically bonded. A heterogeneous mixture is a mixture of two or more chemical substances where the various components can be visually distinguished. A homogeneous mixture is a type of mixture in which the composition is uniform and every part of the solution has the same properties. Various separation techniques exist in order to separate matter, including include distillation, filtration, evaporation and chromatography.
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