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An overview of subatomic particles, including protons, neutrons, and electrons, as well as atomic weights and quantum numbers. Topics covered include the properties of protons, neutrons, and electrons, the concept of atomic weights, and an explanation of quantum numbers and their significance in understanding atomic structure.
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Subatomic Particles A. Protons – Protons carry a single positive charge that have a mass of one approximately one atomic mass unit. The atomic number is equal to the number of protons found in an atom. B. Neutrons – Neutrons carry no charge and have a slightly larger mass than protons. Isotopes of an element have different number of neutrons but the same number of protons. The mass number is equal to the number of protons plus number of neutrons. C. Electrons – Electrons carry a charge equal but opposite to that of protons. An electron is very small, about 1/1, th the mass of a proton. Atomic Weights Atomic mass of an atom is expressed in atomic mass units (amu) which is approximately 1.66x
Js), c is the velocity of light (3.00x 8 m/s) and _ is the wavelength of the radiation. Each element can have its electrons excited to different distinct energy levels, giving each element a unique atomic emission spectrum (like a fingerprint).
Quantum Numbers Bohr’s model assumed that electrons follow a circular orbit at a fixed distance from the nucleus. However, Bohr’s model did not take into consideration of the repulsion between multiple electrons. Using the quantum model, electrons are described as being in regions in space called orbitals, rather than circular orbits. Orbitals show the probability of finding an electron in the atom. The reason why we now use probability is because pinpointing the exact location of an electron is almost impossible as described in Heisenberg uncertainty principle. A. Principal Quantum Number (n)– Also known as the principal energy level, this number can theoretically take on any positive integer value. The larger the value of n, the higher the energy and the radius of the electron’s path. The maximum number of electrons in energy level n is 2n 2 . B. Azimuthal Quantum Number (l) – Also known as the angular momentum, refers to the subshells or sublevels that occur in the principal energy level. For any given energy level n, it can have n-1 sublevels, values being from 0 to n-1. The first four subshells l= 0, 1, 2, and 3 are known as the s, p, d andf subshells. The maximum number of electrons in each subshell is 4l+2. C. Magnetic Quantum Number (ml)– an orbital is a specific region within a subshell that contain no more than two electrons. Each subshell can contain multiple orbitals, but the magnetic quantum number specifies which orbital an electron is likely to be found. Ml can be integers between l and –l, including