{"id":1300,"date":"2016-04-29T20:47:59","date_gmt":"2016-04-29T20:47:59","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/biologyxwaymakerxmaster\/?post_type=chapter&p=1300"},"modified":"2023-07-11T18:09:37","modified_gmt":"2023-07-11T18:09:37","slug":"atoms-and-elements","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/ivytech-wmopen-nmbiology\/chapter\/atoms-and-elements\/","title":{"raw":"Atoms and Elements","rendered":"Atoms and Elements"},"content":{"raw":"

What you\u2019ll learn to do: Define atoms and elements<\/h2>\r\nYou're probably familiar with the concept of atoms. They are the fundamental unit of matter\u2014everything is made up of atoms, which come together in unique ways to form different things. Before you can understand chemical reactions, you must first understand the way that atoms work.\r\n\r\nOver the years, scientists have used different models to visualize atoms as our understanding has changed. You may be familiar with a few of the models in Figure 1. In this course, we we largely use the Bohr model.\r\n\r\n[caption id=\"attachment_5635\" align=\"aligncenter\" width=\"1024\"]\"Four Figure 1. The evolution of atomic models over the years. As our understanding of atoms has evolved, the models we use to depict them have changed. The first model is the Thomson model, followed by the Rutherford model, the Bohr model, and the Heisenberg\/Schr\u00f6dinger model.[\/caption]\r\n\r\n
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Learning Outcomes<\/h3>\r\n
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  • Identify the elements common in biological matter<\/li>\r\n \t
  • Explain the structure and components of an atom<\/li>\r\n \t
  • Identify the properties of elements given a periodic table<\/li>\r\n \t
  • Define the term isotope<\/li>\r\n<\/ul>\r\n<\/div>\r\n

    Elements in Biological Matter<\/h2>\r\nAt its most fundamental level, life is made up of matter. Matter<\/strong> is any substance that occupies space and has mass. Elements<\/strong> are unique forms of matter with specific chemical and physical properties that cannot be broken down into smaller substances by ordinary chemical reactions. There are 118 elements, but only 92 occur naturally. The remaining elements are synthesized in laboratories and are unstable.\r\n
    \r\n\r\nEach element is designated by its chemical symbol, which is a single capital letter or, when the first letter is already \"taken\" by another element, a combination of two letters. Some elements follow the English term for the element, such as C for carbon and Ca for calcium. Other elements' chemical symbols derive from their Latin names; for example, the symbol for sodium is Na, referring to natrium<\/em>, the Latin word for sodium.\r\n\r\nThe four elements common to all living organisms are oxygen (O), carbon (C), hydrogen (H), and nitrogen (N). In the non-living world, elements are found in different proportions, and some elements common to living organisms are relatively rare on the earth as a whole, as shown in Table 1. For example, the atmosphere is rich in nitrogen and oxygen but contains little carbon and hydrogen, while the earth's crust, although it contains oxygen and a small amount of hydrogen, has little nitrogen and carbon. In spite of their differences in abundance, all elements and the chemical reactions between them obey the same chemical and physical laws regardless of whether they are a part of the living or non-living world.<\/em>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
    Table 1. Approximate Percentage of Elements in Living Organisms (Humans) Compared to the Non-living World<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
    Element<\/th>\r\nLife (Humans)<\/th>\r\nAtmosphere<\/th>\r\nEarth's Crust<\/th>\r\n<\/tr>\r\n
    Oxygen (O)<\/td>\r\n65%<\/td>\r\n21%<\/td>\r\n46%<\/td>\r\n<\/tr>\r\n
    Carbon (C)<\/td>\r\n18%<\/td>\r\ntrace<\/td>\r\ntrace<\/td>\r\n<\/tr>\r\n
    Hydrogen (H)<\/td>\r\n10%<\/td>\r\ntrace<\/td>\r\n0.1%<\/td>\r\n<\/tr>\r\n
    Nitrogen (N)<\/td>\r\n3%<\/td>\r\n78%<\/td>\r\ntrace<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n

    Atoms<\/h2>\r\nTo understand how elements come together, we must first discuss the smallest component or building block of an element, the atom. An atom<\/strong> is the smallest unit of matter that retains all of the chemical properties of an element. For example, one gold atom has all of the properties of gold in that it is a solid metal at room temperature. A gold coin is simply a very large number of gold atoms molded into the shape of a coin and containing small amounts of other elements known as impurities. Gold atoms cannot be broken down into anything smaller while still retaining the properties of gold.\r\n\r\n[caption id=\"attachment_1550\" align=\"alignright\" width=\"400\"]\"This Figure 2. Elements, such as helium, depicted here, are made up of atoms. Atoms are made up of protons and neutrons located within the nucleus, with electrons in orbitals surrounding the nucleus.[\/caption]\r\n\r\nAll atoms contain protons, electrons, and neutrons (Figure 2). The only exception is hydrogen (H), which is made of one proton and one electron.\r\n\r\nA proton<\/strong> is a positively charged particle that resides in the nucleus<\/strong> (the core of the atom) of an atom and has a mass of 1 and a charge of +1.\r\n\r\nNeutrons<\/strong>, like protons, reside in the nucleus of an atom. They have a mass of 1 and no charge. The positive (protons) and negative (electrons) charges balance each other in a neutral atom, which has a net zero charge.\r\n\r\nAn electron<\/strong> is a negatively charged particle that travels in the space around the nucleus. In other words, it resides outside of the nucleus. It has a negligible mass and has a charge of \u20131.\r\n\r\nBecause protons and neutrons each have a mass of 1, the mass of an atom is equal to the number of protons and neutrons of that atom. The number of electrons does not factor into the overall mass, because their mass is so small.\r\n
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    Build An Atom<\/h3>\r\nBuild an atom out of protons, neutrons, and electrons, and see how the element, charge, and mass change. Then play a game to test your ideas!\r\n\r\n