![]() ![]() In computer programming, an array is a stored list of individual elements or pieces of data. The term element is used in computing to refer to a smaller component of a larger system. This was eventually refined into what's now known as the periodic table of the elements. He also made predictions about then unknown elements based on his research. In 1869, Dimitri Mendeleev organized the known elements by atomic weight and grouped them according to similar properties. In the early 1800s, John Dalton proposed atomic theory and was able to determine the atomic weights of many elements. He arranged the elements into metallic and non-metallic categories. He defined an element as a simple substance that can't be broken down further and listed many of the elements that we know of today. In 1789, Antoine Lavoisier wrote "Elementary Treatise on Chemistry," which is considered the first modern book on chemistry. In the 1600s, as more of these indivisible substances were discovered, Robert Boyle defined an element as simple substances that can't decompose or be broken down into component substances. Most ancient Greeks believed there were four elements - air, water, earth and fire - while Aristotle defined dry, moist, hot and cold as elements that could be combined to form air, water, earth and fire.Īlchemists identified certain substances - such as lead, gold, mercury and sulfur - that couldn't be changed. The ancient philosopher Plato is credited as the first person to use the term element, from the ancient Greek stoikhe îon – meaning one of a series, component – and the Latin elementum – meaning basic principle or rudiment. People therefore believed that most items could be broken into simpler forms until the smallest indivisible part was reached. The periodic table organizes all elements by atomic number and symbol.įrom ancient times, it was understood that some items could be turned into others, such as a log being burned or a person eating food. Nuclear fusion happens in the heart of a star when hydrogen is fused into helium as the star ages and its gravity increases, it’s crushed into progressively heavier and heavier elements. In nuclear fusion, light elements have their nucleases forced together to form a heavier element. In nuclear reactors, the element uranium is split by collisions with free neutrons that release energy. In nuclear fission, a heavy element with many protons and neutrons is split into lighter elements. The only way to change one element into another is to use a nuclear reaction. ![]() During this entire process, the carbon has gone through many reactions and been in different molecular structures, but it hasn’t changed from one element into another. When the coal is crushed under immense pressure, the carbon atoms are rearranged into a diamond. When the tree is burned, it becomes coal, which is primarily a lump of compressed carbon. ![]() The glucose is then used to form the cellulose of a tree's cell walls. Carbon dioxide is captured by trees and, using the photosynthesis chemical reaction, the carbon is stripped out of the CO 2 molecule and added to a glucose molecule. The carbon atom starts off bonded to oxygen in a carbon dioxide (CO 2) molecule. To illustrate the immutability of an element, imagine a carbon atom. A nuclear reaction is required to alter the nucleus of an atom. Chemical reactions such as burning or bonding into atoms can't alter the nucleus of an atom and can't change an element. The strong nuclear force holds an atom's nucleus together and is difficult to break. The nature and properties of an element are set by the number of protons and neutrons in its nucleus. Atoms combine to form molecules, which are the basis of chemistry.Ĭhemical reactions can't change one element to another. The other 24 elements have been synthesized in particle accelerators and are unable to stay stable for long periods of time these are known as man-made elements. The periodic table of elements has 118 different elements, and 94 of these are known to occur in nature. Na can form an ionic bond with chlorine (Cl) where the sodium loses an electron - becoming Na+ - and gives it to the chlorine atom - which then becomes Cl- to form common table salt. For example, sodium (Na) is a highly reactive element. The same element can also vary in the number of electrons it has, creating ions. ![]() However, all three can be classified as the element hydrogen. For example, common hydrogen has one proton and no neutrons, deuterium has one proton and one neutron, and tritium has one proton and two neutrons. Isotopes will have the same chemical properties, but different physical ones. The number of neutrons in the nucleus can vary, creating isotopes. Each element is classified by the number of protons in its nucleus, known as its atomic number. ![]()
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