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Describe the Relationship the Exist Between the Number of a Period and the Electrons Structures of Atoms of Elements in the Period

Essay by   •  December 8, 2011  •  Essay  •  579 Words (3 Pages)  •  2,485 Views

Essay Preview: Describe the Relationship the Exist Between the Number of a Period and the Electrons Structures of Atoms of Elements in the Period

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1. The periodic table organizes the elements into a grid of horizontal rows called periods and vertical columns called groups. Each group is numbered 1 to 8 and has either an A or a B. The groups that have an A are often referred to as representative elements because of their wide range of chemical and physical properties. The groups that have a B are referred to as transition elements. Elements that are in the same group have similar chemical and physical properties. The elements are placed in certain period in order to determine the number of electrons that are needed in order for the element to be uncreative. The energy level of an elements valence electrons indicates the period in which it can be found. The octet rule describes how each element wants to have 8 electrons on its outer shell so that it will not be reactant.

The atomic size of an atom, also called the atomic radius, refers to the distance between an atom's nucleus and its valence electrons. Moving from left to right across a period, the atomic radius decreases. The nucleus of the atom gains protons moving from left to right, increasing the positive charge of the nucleus and increasing the attractive force of the nucleus upon the electrons.

A cation is positively charged, which means that it is an atom that has lost an electron or electrons. The positive charge of the nucleus is thus distributed over a smaller number of electrons and electron-electron repulsion is decreased, meaning that the electrons are held more tightly and the atomic radius is smaller than in the normal neutral atom.

Anions, are negatively charged ions: atoms that have gained electrons. In anions, electron-electron repulsion increases and the positive charge of the nucleus is distributed over a large number of electrons. Anions have a greater atomic radius than the neutral The process of gaining or losing an electron requires energy.

There are two common ways to measure this energy change: ionization energy and electron affinity. The ionization energy is the energy it takes to fully remove an electron from the atom. When several electrons are removed from an atom, the energy that it takes to remove the first electron is called the first ionization energy, the energy it takes to remove the second electron is the second ionization energy, and so on.

Ionization energy predictably increases moving across the periodic table from left to right. An atom's electron affinity is the energy change in an atom when that atom gains an electron. When an atom gains an electron and becomes more stable, its potential energy decreases: upon gaining an electron the atom gives off energy and the electron affinity is negative. When an atom becomes less stable upon gaining an electron, its potential energy increases, which implies that the atom gains energy as it acquires the electron. Electron affinities becoming increasingly negative from left to right.

Electronegativity

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