4/14/2024 0 Comments Bohr atomic theoryGroup 17 elements, including fluorine and chlorine, have seven electrons in their outermost shells they tend to fill this shell by gaining an electron from other atoms, making them negatively-charged ions. When an atom loses an electron to become a positively-charged ion, this is indicated by a plus sign after the element symbol for example, Na +. As a result of losing a negatively-charged electron, they become positively-charged ions. This means that they can achieve a stable configuration and a filled outer shell by donating or losing an electron. In comparison, the group 1 elements, including hydrogen (H), lithium (Li), and sodium (Na), all have one electron in their outermost shells. Their non-reactivity has resulted in their being named the inert gases (or noble gases). As shown in, the group 18 atoms helium (He), neon (Ne), and argon (Ar) all have filled outer electron shells, making it unnecessary for them to gain or lose electrons to attain stability they are highly stable as single atoms. The periodic table is arranged in columns and rows based on the number of electrons and where these electrons are located, providing a tool to understand how electrons are distributed in the outer shell of an atom. Elements in other groups have partially-filled valence shells and gain or lose electrons to achieve a stable electron configuration.Īn atom may gain or lose electrons to achieve a full valence shell, the most stable electron configuration. A full valence shell is the most stable electron configuration. Group 18 elements (helium, neon, and argon are shown) have a full outer, or valence, shell. The negative sign in Equation 7.3.3 indicates that the electron-nucleus pair is more tightly bound when they are near each other than when they are far apart.\):īohr diagrams indicate how many electrons fill each principal shell. The orbit with n = 1 is the lowest lying and most tightly bound. In his final years, he devoted himself to the peaceful application of atomic physics and to resolving political problems arising from the development of atomic weapons.Īs n decreases, the energy holding the electron and the nucleus together becomes increasingly negative, the radius of the orbit shrinks and more energy is needed to ionize the atom. (b) The energy of the orbit becomes increasingly less negative with increasing n.ĭuring the Nazi occupation of Denmark in World War II, Bohr escaped to the United States, where he became associated with the Atomic Energy Project. The atom has been ionized.įigure 7.3.2 The Bohr Model of the Hydrogen Atom (a) The distance of the orbit from the nucleus increases with increasing n. In this state the radius of the orbit is also infinite. In that level, the electron is unbound from the nucleus and the atom has been separated into a negatively charged (the electron) and a positively charged (the nucleus) ion. In this model n = ∞ corresponds to the level where the energy holding the electron and the nucleus together is zero. Where \( \Re \) is the Rydberg constant, h is Planck’s constant, c is the speed of light, and n is a positive integer corresponding to the number assigned to the orbit, with n = 1 corresponding to the orbit closest to the nucleus.
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