IONS
 

If an atom has more or less electrons than protons, that atom acquires an electric charge. A shortage of electrons results in positive charge; an excess of electrons gives a negative charge. An element’s identity remains the same, no matter how great the excess or shortage of electrons. In the extreme case, all the electrons may be removed from an atom, leaving only the nucleus. This will still represent the same element, however, as it would if it had all its electrons. A electrically charged atom is called an ion. When a substance contains many ions, the material is said to be ionized. If an atom has more electrons than protons, it is a negative ion. If it has fewer electrons than protons, it is a positive ion. If the number of electrons and protons is the same, then the atom is electrically neutral. Ionization can take place when substances are heated to high temperatures or when they are placed in intense electrical fields. Ionization also can occur in substance as a result of exposure to ultraviolet light, x-rays, gamma rays, or high-speed subatomic particles such as neutrons, protons, helium nuclei, or electrons. So-called ionizing radiation, more often called radioactivity, ionizes the atoms in living tissue and can cause illness, death, and genetic mutations. Lightning is the result of ionization of the air. An electric spark is caused by a large buildup of charges, resulting in forces on the electrons in the intervening medium. These forces pull the electrons away from individual atoms. Ionized atoms generally conduct electric currents with greater ease than electrically neutral atoms. The ionization, caused by a powerful electrical field, occurs along a jagged, narrow channel, as you have surely seen. After the lightning flash, the nuclei of the atoms quickly attract stray electrons back, and the air becomes electrically neutral again. An element may be both an ion and an isotope different from the usual isotope. For example, an atom of carbon may have eight neutrons rather than the usual six, thus being the isotope ¹⁴C, and it may have been stripped
of an electron, giving it a positive unit electric charge and making it an ion.The atmosphere of our planet becomes less dense with increasing altitude. Because of this, the amount of ultraviolet and x-ray energy received from the Sun gets greater as we go higher. At certain altitudes, the gases in the atmosphere become ionized by solar radiation. These regions comprise the ionosphere of the Earth. The ionosphere has a significant effect on the propagation of radio waves at certain frequencies. The ionized layers absorb or refract the waves. This makes long-distance communication possible on the so-called shortwave radio bands.

مواضيع ذات صلة

خواص الذرات

البنية الإلكترونية للذرات

الذرات

Linear systems

Confined waves, with natural frequencies

The reflection of waves

Einstein’s laws of radiation

The Boltzmann law

Energy levels

The size of an atom

Bremsstrahlung

Synchrotron radiation