{"id":4330,"date":"2019-06-17T18:00:17","date_gmt":"2019-06-17T18:00:17","guid":{"rendered":"https:\/\/pressbooks.ccconline.org\/acchumanbio\/chapter\/3-2-elements-and-compounds-3\/"},"modified":"2023-11-30T17:48:37","modified_gmt":"2023-11-30T17:48:37","slug":"3-2-elements-and-compounds-3","status":"publish","type":"chapter","link":"https:\/\/pressbooks.ccconline.org\/acchumanbio\/chapter\/3-2-elements-and-compounds-3\/","title":{"raw":"3.2\u00a0Elements and Compounds","rendered":"3.2\u00a0Elements and Compounds"},"content":{"raw":"

What Are You Made of?<\/span><\/h1>\r\n[caption id=\"attachment_250\" align=\"alignleft\" width=\"300\"]\"\" Figure 3.2.1 What are we?<\/em>[\/caption]\r\n\r\nYour entire body is made of cells and cells are made of molecules.If you look at your hand, what do you see? Of course, you see skin, which consists of [pb_glossary id=\"5665\"]cells[\/pb_glossary]<\/strong>. But what are skin cells\u00a0made<\/em>\u00a0of? Like all living\u00a0cells, they are made of matter. In fact,\u00a0all<\/em>\u00a0things are made of matter.\u00a0[pb_glossary id=\"5635\"]Matter[\/pb_glossary]<\/strong>\u00a0is anything that takes up space and has mass. Matter, in turn, is made up of chemical substances. A\u00a0[pb_glossary id=\"5731\"]chemical substance[\/pb_glossary]<\/strong>\u00a0is matter that has a definite\u00a0composition\u00a0that is\u00a0consistent\u00a0throughout. A chemical substance may be either an\u00a0element\u00a0or a\u00a0compound.\r\n

Elements and Atoms<\/h1>\r\nAn\u00a0[pb_glossary id=\"5747\"]element[\/pb_glossary]<\/strong>\u00a0is a\u00a0pure substance. It cannot be broken down into other types of substances. Each\u00a0element\u00a0is made up of just one type of\u00a0[pb_glossary id=\"5711\"]atom[\/pb_glossary]<\/strong>.\r\n

Structure of an\u00a0Atom<\/h2>\r\n[caption id=\"attachment_253\" align=\"alignright\" width=\"226\"]\"Diagram Figure 3.2.2 An atom consists of three subatomic components: protons, neutrons and electrons.<\/em>[\/caption]\r\n\r\nAn\u00a0[pb_glossary id=\"5711\"]atom[\/pb_glossary]<\/strong> is the smallest particle of an element that still has the properties of that element. Every substance is composed of atoms. Atoms are extremely small, typically about a ten-billionth of a metre in diametre. However, atoms do not<\/em> have well-defined boundaries, as suggested by the atomic model shown\u00a0below.\r\n
\r\n\r\nEvery [pb_glossary id=\"5711\"]atom[\/pb_glossary]<\/strong> is composed of a central area \u2014 called the\u00a0<\/span>[pb_glossary id=\"5717\"]nucleus[\/pb_glossary]<\/strong>\u00a0\u2014 and one or more subatomic particles called [pb_glossary id=\"5751\"]electrons[\/pb_glossary]<\/strong>, which move around the nucleus. The nucleus\u00a0<\/span>also<\/em>\u00a0consists of subatomic particles. It contains one or more [pb_glossary id=\"5823\"]proton[\/pb_glossary]<\/strong>s and typically a similar number of [pb_glossary id=\"5795\"]neutrons[\/pb_glossary]<\/strong>. The number of protons in the\u00a0<\/span>nucleus\u00a0determines the type of element an atom represents. An atom of hydrogen, for example, contains just one\u00a0<\/span>proton. Atoms of the same element may have different numbers of neutrons in the nucleus. Atoms of the same element with the same number of protons \u2014 but different numbers of neutrons \u2014 are called\u00a0<\/span>[pb_glossary id=\"5767\"]isotopes[\/pb_glossary].<\/strong>\r\n\r\n<\/div>\r\nProtons have a positive electric charge and neutrons have no electric charge. Virtually all of an atom's mass is in the protons and neutrons in the\u00a0nucleus. Electrons surrounding the nucleus have almost no mass,\u00a0as well as\u00a0a negative electric charge. If the number of protons and electrons in an atom are equal, then an atom is electrically neutral, because the positive and negative charges cancel each other out. If an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively, and it is called an\u00a0[pb_glossary id=\"5765\"]ion[\/pb_glossary]<\/strong>.<\/strong>\r\n\r\nThe negatively-charged electrons of an atom are attracted to the positively-charged protons in the nucleus by a force called\u00a0[pb_glossary id=\"5745\"]electromagnetic force[\/pb_glossary],<\/strong>\u00a0for which opposite charges attract. Electromagnetic force between protons in the nucleus causes these subatomic particles to repel each other, because they have the same charge. However, the protons and neutrons in the nucleus are attracted to each other by a different force, called\u00a0[pb_glossary id=\"5787\"]nuclear force[\/pb_glossary],<\/strong>\u00a0which is usually stronger than the electromagnetic force. Nuclear force repels the positively-charged protons from each other.\r\n

Periodic Table of the Elements<\/h2>\r\nThere are almost 120 known elements. As you can see in the Periodic Table of the Elements shown\u00a0below, the majority of elements are\u00a0metals. Examples of metals are iron (Fe) and copper (Cu). Metals are shiny and good conductors of electricity and\u00a0heat. Nonmetal elements are far fewer in number. They include hydrogen (H) and oxygen (O). They lack the properties of metals.\r\n
\r\n\r\n\u00a0The periodic table of the elements arranges elements in groups based on their properties. The element most important to life is carbon (C). Find carbon in the table. What type of element is it: metal or nonmetal?\r\n\r\n<\/div>\r\n
\r\n\r\n[caption id=\"attachment_259\" align=\"aligncenter\" width=\"573\"]\"The Figure 3.2.3 The Periodic Table of Elements.<\/em>[\/caption]\r\n

Compounds and Molecules<\/h2>\r\n<\/div>\r\nA\u00a0[pb_glossary id=\"5733\"]compound[\/pb_glossary]<\/strong>\u00a0is a unique substance that consists of two or more elements combined in fixed proportions. This means that the\u00a0composition\u00a0of a\u00a0compound\u00a0is always the same. The smallest particle of most compounds in living things is called a\u00a0[pb_glossary id=\"5779\"]molecule[\/pb_glossary].<\/strong>\r\n\r\n[caption id=\"attachment_285\" align=\"alignright\" width=\"256\"]\"Image Figure 3.2.4 A molecule of water consists of one atom of oxygen and two atoms of hydrogen connected by covalent bonds.<\/em>[\/caption]\r\n\r\nConsider\u00a0water\u00a0as an example. A molecule of water always contains one atom of oxygen and two atoms of hydrogen. The\u00a0composition\u00a0of water is expressed by the\u00a0chemical formula\u00a0H2<\/sub>O. A model of a water molecule is shown in Figure 3.2.4.\r\n\r\nWhat causes the atoms of a\u00a0water\u00a0molecule to \u201cstick\u201d together? The answer is\u00a0chemical bonds<\/em>. A\u00a0[pb_glossary id=\"5727\"]chemical bond[\/pb_glossary]<\/strong>\u00a0is a force that holds together the atoms of molecules. Bonds in molecules involve the sharing of electrons among atoms. New\u00a0chemical bonds\u00a0form when substances react with one another. A\u00a0[pb_glossary id=\"5729\"]chemical reaction[\/pb_glossary]<\/strong>\u00a0is a process that changes some chemical substances into others. A\u00a0chemical reaction\u00a0is needed to form a compound, and another chemical reaction is needed to separate the substances in that compound.\r\n\r\n \r\n
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3.2 Summary<\/span><\/h1>\r\n<\/header>\r\n
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