{"id":23566,"date":"2019-05-15T15:05:47","date_gmt":"2019-05-15T15:05:47","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=23566"},"modified":"2023-06-07T18:54:29","modified_gmt":"2023-06-07T18:54:29","slug":"chemical-properties-of-atoms","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/atom-properties-of-atoms\/chemical-properties-of-atoms\/","title":{"rendered":"Chemical Properties of Atoms"},"content":{"rendered":"
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Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. The chemical properties of the atom<\/strong> are determined by the number of protons, in fact, by the number and arrangement of electrons. The configuration of these electrons follows the principles of quantum mechanics. The number of electrons in each element\u2019s electron shells, particularly the outermost valence shell, is the primary factor determining its chemical bonding behavior. In the periodic table, the elements are listed in order of increasing atomic number Z.<\/p>\n

The total number of protons in the nucleus of an atom is called the atomic number<\/strong> (or the proton number<\/strong>) of the atom and is given the symbol Z<\/strong>. The number of electrons in an electrically-neutral atom is the same as the number of protons in the nucleus. Therefore, the total electrical charge of the nucleus is +Ze<\/strong>, where e (elementary charge) equals 1,602 x 10<\/strong>-19<\/sup><\/strong>coulombs<\/strong>. Each electron is influenced by the electric fields produced by the positive nuclear charge and the other (Z \u2013 1) negative electrons in the atom.<\/p>\n

The Pauli exclusion principle<\/strong><\/a> requires the electrons in an atom to occupy different energy levels instead of them all condensing in the ground state. The ordering of the electrons in the ground state of multielectron atoms starts with the lowest energy state (ground state). It moves progressively up the energy scale until each atom\u2019s electrons have been assigned a unique set of quantum numbers. This fact has key implications for building up the periodic table of elements.<\/p>\n<\/div><\/div>

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Electron Affinity<\/h2>\n

In chemistry and atomic physics, the electron affinity<\/strong> of an atom or molecule is defined as:<\/p>\n

the change in energy (in kJ\/mole) of a neutral atom or molecule (in the ga搜索引擎优化us phase) when an electron is added to the atom to form a negative ion<\/em>.<\/p>\n

X + e\u2013<\/sup> \u2192 X\u2013<\/sup> + energy \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Affinity = \u2013 \u2206H<\/strong><\/p>\n

In other words, it can be expressed as the neutral atom\u2019s likelihood of gaining an electron. Note that ionization energies measure the tendency of a neutral atom to resist the loss of electrons. Electron affinities<\/strong> are more difficult to measure than ionization energies.<\/p>\n

A fluorine atom in the gas phase, for example, gives off energy when it gains an electron to form a fluoride ion.<\/p>\n

F + e\u2013<\/sup> \u2192 F\u2013<\/sup> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u2013 \u2206H = Affinity = 328 kJ\/mol<\/strong><\/p>\n

It is essential to keep track of signs to use electron affinities<\/strong> properly. When an electron is added to a neutral atom, energy is released. This affinity is known as the first electron affinity,<\/strong> and these energies are negative. By convention, the negative sign shows a release of energy. However, more energy is required to add an electron to a negative ion which overwhelms any release of energy from the electron attachment process. This affinity is known as the second electron affinity,<\/strong> and these energies are positive.<\/p>\n

Affinities of Nonmetals vs. Affinities of Metals<\/h2>\n