Figure 1. Generalized energy-level diagram for atomic orbitals in an atom with two or more electrons (not to scale). Source: OpenStax Chemistry 2e Orbital Energies and Atomic Structure (OpenStax Chemistry 2e) The energy of atomic orbitals increases as the principal quantum number, n, increases. In any atom with two or more electrons, the repulsion between the electrons … Continue reading Orbital Energies and Atomic Structure

Source: OpenStax Chemistry 2e The Pauli Exclusion Principle (OpenStax Chemistry 2e) An electron in an atom is completely described by four quantum numbers: n, l, ml, and ms. The first three quantum numbers define the orbital and the fourth quantum number describes the intrinsic electron property called spin. An Austrian physicist Wolfgang Pauli formulated a general principle that gives … Continue reading The Pauli Exclusion Principle

Figure 1. Different shells are numbered by principal quantum numbers. Source: OpenStax Chemistry 2e Quantum Theory of Electrons (OpenStax Chemistry 2e) The goal of this section is to understand the electron orbitals (location of electrons in atoms), their different energies, and other properties. The use of quantum theory provides the best understanding to these topics. This knowledge … Continue reading Understanding Quantum Theory of Electrons in Atoms

Source: https://pixabay.com/illustrations/atom-chemistry-science-model-1674878/ The Quantum–Mechanical Model of an Atom (OpenStax Chemistry 2e) Shortly after de Broglie published his ideas that the electron in a hydrogen atom could be better thought of as being a circular standing wave instead of a particle moving in quantized circular orbits, Erwin Schrödinger extended de Broglie’s work by deriving what is … Continue reading The Quantum–Mechanical Model of an Atom

Figure 1. An interference pattern on the water surface is formed by interacting waves. The waves are caused by reflection of water from the rocks. (credit: modification of work by Sukanto Debnath) Behavior in the Microscopic World (OpenStax Chemistry 2e) We know how matter behaves in the macroscopic world—objects that are large enough to be seen by … Continue reading Behavior in the Microscopic World

Figure 1. Quantum numbers and energy levels in a hydrogen atom. The more negative the calculated value, the lower the energy. Source: OpenStax Chemistry 2e The Bohr Model (OpenStax Chemistry 2e) Following the work of Ernest Rutherford and his colleagues in the early twentieth century, the picture of atoms consisting of tiny dense nuclei surrounded by lighter and even … Continue reading The Bohr Model

Figure 1. Neon signs operate by exciting a gas at low partial pressure using an electrical current. This sign shows the elaborate artistic effects that can be achieved. (credit: Dave Shaver) Line Spectra (OpenStax Chemistry 2e) When solids, liquids, or condensed gases are heated sufficiently, they radiate some of the excess energy as light. Photons produced … Continue reading Line Spectra

Photons with low frequencies do not have enough energy to cause electrons to be ejected via the photoelectric effect. For any frequency of light above the threshold frequency, the kinetic energy of an ejected electron will increase linearly with the energy of the incoming photon. Source: OpenStax Chemistry 2e The Photoelectric Effect (OpenStax Chemistry 2e) … Continue reading The Photoelectric Effect

Figure 1. The spectral distribution (light intensity vs. wavelength) of sunlight reaches the Earth's atmosphere as UV light, visible light, and IR light. The unabsorbed sunlight at the top of the atmosphere has a distribution that approximately matches the theoretical distribution of a blackbody at 5250 °C, represented by the blue curve. (credit: modification of work … Continue reading Blackbody Radiation and the Ultraviolet Catastrophe

By Unknown - http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1964/, https://en.wikipedia.org/w/index.php?curid=34665020 Dorothy Hodgkin (OpenStax Chemistry 2e) The wavelengths of X-rays (10-10,000 picometers [pm]) are comparable to the size of atoms, X-rays can be used to determine the structure of molecules. When a beam of X-rays is passed through molecules packed together in a crystal, the X-rays collide with the electrons and … Continue reading Dorothy Hodgkin (1910-94)