Two of the subatomic particles have electric charges: protons have a positive charge, while electrons have a negative charge. Neutrons, on the other hand, have no charge. A rule of thumb is that particles with the same charge are repelled from each other, while particles of opposite charges are attracted to each other. Similar to the opposite ends of a magnet, protons and electrons are attracted to each other. Just like a resistor that tries to squeeze the same ends of two magnets, protons are repelled by other protons and electrons by other electrons. The (PageIndex{1}) table specifies the properties and positions of electrons, protons, and neutrons. The second column shows the masses of the three subatomic particles in “atomic mass units”. An atomic unit of mass ((text{amu})) is defined as one twelfth of the mass of a carbon-12 atom. Atomic mass units ((text{amu})) are useful because, as you can see, the mass of a proton and the mass of a neutron in this system of units are almost exactly (1.0). Electrons are one of the three main types of particles that make up atoms. The other two types are protons and neutrons.
Unlike protons and neutrons, which are made up of smaller, simpler particles, electrons are fundamental particles that are not made up of smaller particles. They are a type of fundamental particle called leptons. All leptons have an electrical charge of (-1) or (0). Electrons are extremely small. The mass of an electron is only about 1/2000 of the mass of a proton or neutron, so electrons practically do not contribute to the total mass of an atom. Electrons have an electric charge of (-1), which is equal to but opposite to the charge of a proton, which is (+1). All atoms have the same number of electrons as protons, so positive and negative charges “cancel each other out,” making atoms electrically neutral. Well, while the protons of an element are the same, the number of neutrons can vary from atom to atom. The number of neutrons determines the isotope of an atom. This is important for NRC because the number of neutrons relative to protons determines the stability of the nucleus, with some isotopes undergoing radioactive decay.
Although radioactive decay can occur in a variety of ways, it is, in simple terms, the process by which unstable atoms decay and release particles (and energy). The atoms of all elements – with the exception of most hydrogen atoms – have neutrons in their nucleus. Unlike protons and electrons, which are electrically charged, neutrons have no charge – they are electrically neutral. Therefore, neutrons are marked with (n^0) in the diagram above. Zero means “zero charge”. The mass of a neutron is slightly greater than the mass of a proton, which is 1 atomic mass unit (left( text{amu} right)). (One atomic mass unit is equivalent to about (1.67 times 10^{-27}) kilograms.) A neutron is also about the same diameter as a proton or (1.7 by 10^{17}) meters. Two atoms with an identical number of protons in their nuclei belong to the same element. An element such as hydrogen, oxygen or iron is a substance that cannot be broken down into anything else apart from a nuclear reaction. In other words, one element cannot be transformed into another (again, with the exception of nuclear reactions).
Unlike protons and neutrons, which are located in the nucleus in the middle of the atom, electrons are located outside the nucleus. Since the opposite electric charges attract each other, the negative electrons are attracted to the positive nucleus. This gravitational pull keeps electrons in constant motion in the otherwise empty space around the nucleus. The following figure is a common way of representing the structure of an atom. It shows the electron as a particle orbiting the nucleus, much like planets orbit the sun. However, this is a bad prospect because electrons are more complicated, as shown by quantum mechanics. Dalton`s atomic theory explained much about matter, chemicals, and chemical reactions. Still, this wasn`t entirely accurate, because contrary to what Dalton believed, atoms can actually be broken down into smaller subunits or subatomic particles. We talked about the electron in detail, but there are two other particles of interest: protons and neutrons. We have already learned that J.
J. Thomson discovered a negatively charged particle called the electron. Rutherford suggested that these electrons orbit a positive nucleus. In later experiments, he discovered that there is a smaller, positively charged particle in the nucleus called a proton. There is a third subatomic particle known as the neutron. Negative and positive charges of the same magnitude cancel each other out. This means that the negative charge of an electron perfectly balances the positive charge on the proton. In other words, a neutral atom must have exactly one electron for every proton. If a neutral atom has 1 proton, it must have 1 electron. If a neutral atom has 2 protons, it must have 2 electrons.
If a neutral atom has 10 protons, it must have 10 electrons. You have the idea. To be neutral, an atom must have the same number of electrons and protons. .
