Electrons

We will today discover the details of the electron and how important it is.

Definition
The electron is a subatomic particle that carries a negative charge or a single unit of negative electrivity.
Electrons
We know all mater consists of atoms that contain three subatomic particles known as: protons, neutrons, and electrons. Of these three particles, only the electron are to be fundamental particles that is incapable of being broken down into simpler particles. The absence or presence of an excess of electrons is responsible for all electrical phenomena. It makes most of everything that we know, with the proton and neutron. Suppose you look at a battery, you see a plus and a minus, well that tells you.
Energy
The nucleus of an atom is the part consisting of the protons and neutrons. The size of the nucleus is many thousands of times smaller than the size of the whole atom. Electrons are distributed in specific regions outside the nucleus. At one time, scientist thought that electron traveled in very specific pathways around the nucleus, similar to the orbits of the planets in the solar system.
Vocabulary
Energy Level - A region of the atom in which there is a high probability of finding electrons.
Positron - The antiparticle of the electron. It has the same mass and spin, but it charge, though equal in magnitude, is opposite in sign to that of the electron.
Electric current - A flow of electrons


The uncertainty principle, a fundamental law of physics, says that the pathway traveled by very small particles like an electron can never be defined perfectly. Instead, scientists now talk about the probability of finding an electron in an atom. In some regions of the atom, that probability is very high, although never 100 percent, and in other regions it is very low, but never 0 percent. The regions in space where the probability of finding an electron is high corresponds roughly to the orbits about which scientists talked earlier. Those regions are now called energy levels.


Properties
Electrons have three properties, charge, mass, and spin. By definition, the electric charge on an electron is   -1. The mass of an electron is 9.109389 x 10^-31 kilograms. Electrons spin on their axis. Spinning , electrons, with a moving electric charge, create a magnetic field around them. This always changes the way the arrange themselves and how they react with each other in atoms.
History and Discovery
In the 1800's, scientist made made a few important basic discoveries about electrical phenomena. But no one could explain the fundamental nature of electricity. In 1897, English Physicist J. J. Thomson that discovered the electron. He showed that the flow of the electric current consisted of individual particles. Thomson obtained the same result using a number of materials and concluded these particles (electrons) are  present in all forms of matter. The name of the particles had been suggested a few years earlier by Irish physicist George Johnstone Stoney.Although Thomson was able to measure the ratio of electric charge of mass (e/m) for an electron, he did not know how to determine either of these two quantities individually. That problem puzzled physicists for more than a decade. Finally, the riddle was solved by American physicist Robert Andrew Millikan (1868–1953) in a series of experiments conducted between 1907 and 1913. The accompanying figure outlines the main features of Millikan's famous oil drop experiment.

The oil drops needed for the experiment are produced by a common squeeze-bulb atomizer. The tiny droplets formed by this method fall downward and through the hole in the upper plate under the influence of gravity. As they fall, the droplets are given a negative electric charge. Once droplets enter the space between the two plates, the highvoltage source is turned on. The negatively charged oil droplets are then attracted upward by the positive charge on the upper metal plate. At this point, the droplets are being tugged by two opposite forces: gravity, pulling them downward, and an electrical force, pulling them upward. By carefully adjusting the voltage used, Millikan was able to keep oil droplets suspended in space between the two plates. Since the droplets moved neither upward or downward, he knew that the gravitational force on the droplets was exactly matched by the electric force. From this information, he was able to calculate the value of the electric charge on a droplet. The result he obtained, a charge of 1.591 × 10⁻¹⁰ coulomb, is very close to the value accepted today of 1.602177 × 10⁻¹⁹ coulomb. (The coulomb is the standard metric unit of electrical charge.)  

Electron Mail

How would you send a letter to an electron? As strange as that question seems, electrons have "addresses," just as people do. Think of an oxygen atom, for example. Every oxygen atom has eight electrons. But those eight electrons are all different from each other. The differences among the eight electrons are represented by quantum numbers. A quantum number is a number that describes some physical property of an object (in this case, of an electron). We know that any electron can be completely described by stating four of its properties. Those properties are represented by four different quantum numbers represented by the letters n, ℓ, m_ℓ, and s. Quantum number n, for example, represents the distance of an electron from the nucleus. Any electron for which n = 1 is in the first orbit around the nucleus of the atom. Quantum number ℓ represents the shape of the electron's orbit, that is, how flattened out its orbit is. Quantum number m_ℓ represents the magnetic properties of the electron. And quantum number s represents the spin of the electron, whether it's spinning in a clockwise or counter-clockwise direction. So if you decide to send a letter to electron X, whose quantum numbers are 3, 2, 0, + ½, you know it will go to an electron in the third orbit, with a flattened orbital path, certain magnetic properties, and a clockwise spin.

Positron
Dirac's prediction was confirmed only two years after he announced his hypothesis. American physicist Carl David Anderson (1905–1991) found positively charged electrons in a cosmic ray shower that he was studying. Anderson called these particles positrons, for positive electrons. Today, scientists understand that positrons are only one form of antimatter, particles similar to fundamental particles such as the proton, neutron, and electron, but with one property opposite to that of the fundamental particle. One of the interesting detective stories in science involves the discovery of an electron-type particle called the positron. During the 1920s, English physicist Paul Dirac (1902–1984) was using the new tools of quantum mechanics to analyze the nature of matter. Some of the equations he solved had negative answers. Those answers troubled him since he was not sure what a negative answer—the opposite of some property—could mean. One way he went about explaining these answers was to hypothesize the existence of a twin of the electron. The twin would have every property of the electron itself, Dirac said, except for one: it would carry a single unit of positive electricity rather than a single unit of negative electricity.