The ionized form of fluorine is called fluoride, and is written as F –. When it does, its electrons will outnumber its protons by one, and it will have an overall negative charge. Thus, it is highly likely to bond with other atoms in such a way that fluorine accepts one electron (it is easier for fluorine to gain one electron than to donate seven electrons). Its atomic number is nine, and it has seven electrons in its valence shell. Now consider fluorine (F), a component of bones and teeth. A positively charged ion is known as a cation. A potassium ion is written K +, indicating that it has lost a single electron. In other words, the resulting potassium ion will be slightly positive. (It is easier for potassium to donate one electron than to gain seven electrons.) The loss will cause the positive charge of potassium’s protons to be more influential than the negative charge of potassium’s electrons. This characteristic makes potassium highly likely to participate in chemical reactions in which it donates one electron. It has just one electron in its valence shell. Potassium (K), for instance, is an important element in all body cells. What happens to the charged electroscope when a conductor is moved between its plastic sheets, and why? Visit this website to learn about electrical energy and the attraction/repulsion of charges. An atom that has an electrical charge-whether positive or negative-is an ion. This can happen either by gaining electrons to fill a shell that is more than half-full, or by giving away electrons to empty a shell that is less than half-full, thereby leaving the next smaller electron shell as the new, full, valence shell. This happens frequently for most atoms in order to have a full valence shell, as described previously. But when an atom participates in a chemical reaction that results in the donation or acceptance of one or more electrons, the atom will then become positively or negatively charged. As long as this situation remains, the atom is electrically neutral. Recall that an atom typically has the same number of positively charged protons and negatively charged electrons. These are ionic bonds, covalent bonds, and hydrogen bonds. Three types of chemical bonds are important in human physiology, because they hold together substances that are used by the body for critical aspects of homeostasis, signaling, and energy production, to name just a few important processes. Thus, a unit of water, or H 2O, is a compound, as is a single molecule of the gas methane, or CH 4. When a molecule is made up of two or more atoms of different elements, it is called a chemical compound. The bonded atoms may be of the same element, as in the case of H 2, which is called molecular hydrogen or hydrogen gas. A more or less stable grouping of two or more atoms held together by chemical bonds is called a molecule. The new grouping is typically more stable-less likely to react again-than its component atoms were when they were separate. A bond is a weak or strong electrical attraction that holds atoms in the same vicinity. Instead, atoms link by forming a chemical bond. So when you read about atoms linking together or colliding, bear in mind that the atoms are not merging in a physical sense. No force within the human body-or anywhere in the natural world-is strong enough to overcome this electrical repulsion. But do atoms ever actually touch one another? Most physicists would say no, because the negatively charged electrons in their valence shells repel one another. Explain how water molecules link via hydrogen bondsĪtoms separated by a great distance cannot link rather, they must come close enough for the electrons in their valence shells to interact.Distinguish between nonpolar and polar covalent bonds.Identify the key difference between ionic and covalent bonds.Distinguish between ions, cations, and anions.Explain the relationship between molecules and compounds.By the end of this section, you will be able to:
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