Atoms are the building blocks of everything around us. They're made up of tiny particles - protons, neutrons, and electrons - arranged in specific ways. Understanding how atoms work is key to grasping the nature of matter and energy in the universe.
Electrons in atoms can jump between energy levels, absorbing or releasing light in the process. This behavior explains why different elements have unique colors and spectra. It's also crucial for understanding how stars shine and how we can study distant objects in space.
Atomic Structure
Structure of atoms
Atoms fundamental building blocks of matter composed of subatomic particles (protons, neutrons, electrons)
located at the center of the contains protons with positive charge and neutrons with no charge
contains vast majority of atom's mass (99.9%)
Electrons negatively charged particles orbit nucleus in shells or energy levels
in outermost determines atom's chemical properties and behavior (reactivity, bonding)
The number of electrons in the outermost shell, known as , is particularly important for chemical reactions
Electron energy transitions
Electrons occupy discrete energy levels or shells around nucleus labeled with integers (n = 1, 2, 3)
Lower energy levels closer to nucleus (n = 1) have lower potential energy
Each consists of one or more orbitals, which are regions where electrons are likely to be found
Electrons transition between energy levels by absorbing or emitting energy
: moves from lower to higher requires input of energy equal to difference between levels
: electron moves from higher to lower energy level releases energy as with specific wavelength
Electron transitions result in formation of atomic spectra
Emission spectra: unique patterns of light emitted by element (hydrogen spectrum)
Absorption spectra: dark lines in continuous spectrum caused by electrons absorbing specific wavelengths ( in solar spectrum)
Isotopes and atomic properties
are atoms of same element with different numbers of neutrons but same number of protons and electrons
Isotopes denoted by (A) = number of protons + neutrons (Carbon-12 has 6 protons + 6 neutrons, Carbon-14 has 6 protons + 8 neutrons)
Isotopes have similar chemical properties but may differ in physical properties
Some isotopes unstable and undergo (carbon-14, uranium-235)
: emission of alpha particle (helium-4 nucleus)
: emission of beta particle (electron) and antineutrino
: emission of high-energy photons
Isotopic abundances used to determine average of element
Calculated by weighted average of masses of element's isotopes (chlorine-35 at 75.8%, chlorine-37 at 24.2%)
Atomic models and quantum mechanics
The proposed a nuclear atom with electrons orbiting a small, dense nucleus
The introduced the concept of discrete electron energy levels but was later superseded
provides a more accurate description of atomic behavior, including the probabilistic nature of electron positions and the concept of wave-particle duality
The , which is the number of protons in an atom's nucleus, uniquely identifies each element
Key Terms to Review (39)
Absorption: Absorption is the process by which atoms or molecules take in or incorporate other atoms, molecules, or ions. It is a fundamental concept in the structure of the atom, as it describes how atoms can gain or lose electrons, protons, and other subatomic particles to achieve a more stable configuration.
Absorption Spectrum: An absorption spectrum is a unique pattern of dark lines or bands observed in the continuous spectrum of light that has passed through a gaseous substance. These absorption lines correspond to specific wavelengths of light that have been absorbed by the atoms or molecules in the gas, providing valuable information about the chemical composition of the gas.
Alpha Decay: Alpha decay is a type of radioactive decay where an atomic nucleus emits an alpha particle, which is a helium nucleus consisting of two protons and two neutrons. This process results in the transformation of the original atom into a new element with a lower atomic number.
Atom: An atom is the fundamental unit of matter that makes up all elements in the universe. It is the smallest possible division of an element that retains its chemical properties. Atoms are the building blocks of the universe, and understanding their structure and behavior is crucial in the study of the very small scale of the physical world.
Atomic Mass: Atomic mass is the average mass of an atom of a given element, typically measured in atomic mass units (u) or daltons (Da). It is a fundamental property that describes the weight of an individual atom and is a crucial concept in understanding the structure and behavior of atoms and molecules within the context of the universe and the atom.
Atomic Number: The atomic number is a fundamental property of an element that represents the number of protons in the nucleus of an atom. It is a unique identifier for each element and is a crucial concept in understanding the structure of the atom and the periodic table of elements.
Atomic Spectrum: The atomic spectrum refers to the unique pattern of light emitted or absorbed by an atom when its electrons transition between different energy levels. This spectrum provides valuable information about the structure and composition of atoms, which is a fundamental aspect of understanding the nature of matter and energy.
Beta Decay: Beta decay is a type of radioactive decay where a neutron in the nucleus of an atom is converted into a proton, an electron, and an antineutrino. This process occurs in unstable atomic nuclei and is one of the fundamental ways that radioactive elements can become more stable.
Bohr: Bohr refers to Niels Bohr, a physicist who developed the Bohr model of the atom. This model introduced the idea of quantized energy levels for electrons within an atom.
Bohr Model: The Bohr model is a representation of the atom that describes the structure and behavior of electrons within an atom. It was developed by Danish physicist Niels Bohr in 1913 and provided a significant advancement in the understanding of atomic structure.
Electron: An electron is a subatomic particle that carries a negative electric charge and is found in all atoms, orbiting the nucleus. Electrons play a crucial role in the structure of the atom and the formation of spectral lines, which are essential concepts in the study of the very small universe and the nature of matter.
Electron Configuration: Electron configuration is the arrangement and distribution of electrons in an atom's orbitals. It describes the specific energy levels and sublevels occupied by the electrons, providing insight into an atom's chemical properties and behavior.
Emission: Emission refers to the process by which atoms or molecules release energy in the form of electromagnetic radiation or particles. This phenomenon is a fundamental aspect of the structure of the atom and is crucial for understanding various physical and astronomical phenomena.
Emission Spectrum: An emission spectrum is a unique pattern of wavelengths or frequencies of electromagnetic radiation emitted by an atom or molecule when it undergoes a transition from a higher energy state to a lower energy state. This spectrum is a fingerprint that can be used to identify the composition of celestial objects and the elements present in various materials.
Energy level: Energy levels are the fixed energies that electrons can have within an atom. These levels determine the electron's distance from the nucleus and influence atomic interactions.
Energy Level: An energy level is a discrete state of an atom or molecule in which the electrons have a specific amount of energy. The energy levels of an atom or molecule are quantized, meaning they can only take on certain fixed values rather than a continuous range of values. The arrangement and occupancy of these energy levels determine the chemical and physical properties of the atom or molecule.
Energy Transition: Energy transition refers to the shift from one form of energy to another, typically from traditional fossil fuels to more sustainable and renewable energy sources. This process involves changes in the way energy is produced, distributed, and consumed, with the goal of reducing environmental impact and increasing energy efficiency.
Fraunhofer Lines: Fraunhofer lines are dark absorption lines that appear in the continuous spectrum of sunlight and other stars. These lines are caused by the absorption of specific wavelengths of light by elements present in the outer layers of the Sun and other stars, providing valuable information about their chemical composition.
Gamma Decay: Gamma decay is a type of radioactive decay in which an atomic nucleus emits a high-energy electromagnetic radiation called a gamma ray. This process occurs when an excited nucleus transitions to a lower energy state, releasing the excess energy in the form of a gamma photon.
Isotope: An isotope is a variant of a chemical element that has the same number of protons in its nucleus but a different number of neutrons. This results in atoms of the same element having different atomic masses, while maintaining the same atomic number and chemical properties.
Isotopes: Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons in their nuclei. They have nearly identical chemical properties but differ in atomic mass and physical properties.
Mass Number: The mass number, also known as the nucleon number, is the total number of protons and neutrons in the nucleus of an atom. It is a fundamental property that determines the overall mass of an atom and is used to identify the specific isotope of an element.
Neutron: A neutron is a subatomic particle that has no electric charge and a mass slightly greater than that of a proton. Neutrons are found in the nuclei of all atoms, except for the lightest isotope of hydrogen, and play a crucial role in the structure and stability of atomic nuclei across the topics of the Universe of the Very Small, the Structure of the Atom, and the Formation of Spectral Lines.
Neutron star: A neutron star is a highly dense remnant of a massive star that has undergone a supernova explosion. It consists almost entirely of neutrons and has an incredibly strong gravitational field.
Nucleus: The nucleus is the central core of an atom, containing protons and neutrons. It is positively charged and holds most of the atom's mass.
Nucleus: The nucleus is the central and most important part of an atom, containing protons and neutrons. It is the core of an atom that holds the majority of its mass and positive charge, and it is the defining feature of an atom's identity and properties.
Orbital: In the context of atomic structure, an orbital refers to a specific region or path within an atom where an electron is most likely to be found. Orbitals describe the probability distribution of an electron around the nucleus of an atom and are a fundamental concept in quantum mechanics.
Photon: A photon is a quantum of electromagnetic radiation, essentially a particle of light. It has no mass, carries energy, and travels at the speed of light in a vacuum.
Photon: A photon is a fundamental particle that is the basic unit of light and all other forms of electromagnetic radiation. It is the smallest possible quanta, or discrete packet, of electromagnetic energy. Photons are essential to the understanding of the electromagnetic spectrum, spectroscopy in astronomy, and the structure of the atom.
Proton: A proton is a subatomic particle that is the positively charged core of an atom, making up the majority of an atom's mass. Protons are fundamental to the structure and behavior of atoms, which are the building blocks of all matter in the universe.
Quantum mechanics: Quantum mechanics is the branch of physics that studies the behavior of particles at atomic and subatomic levels using principles like wave-particle duality and quantization. It provides the theoretical framework necessary to understand phenomena such as the early universe's conditions and particle interactions during the Big Bang.
Quantum Mechanics: Quantum mechanics is a fundamental theory in physics that describes the behavior of matter and energy on the atomic and subatomic scale. It is the foundation for understanding the structure of atoms, the formation of spectral lines, the evidence for black holes, and the anthropic principle, which explores the relationship between the laws of physics and the existence of life in the universe.
Radioactive decay: Radioactive decay is the process by which an unstable atomic nucleus loses energy by emitting radiation. This can include the release of alpha particles, beta particles, or gamma rays.
Radioactive Decay: Radioactive decay is the process by which an unstable atomic nucleus spontaneously emits radiation in the form of particles or energy, transforming the nucleus into a more stable configuration. This phenomenon is fundamental to understanding the structure of the atom, the evolution of planets, and the relationship between mass and energy in the theory of relativity.
Rutherford: Rutherford is best known for his gold foil experiment, which led to the discovery of the atomic nucleus. His work laid the foundation for modern atomic theory and our understanding of atomic structure.
Rutherford Model: The Rutherford model, also known as the nuclear model of the atom, was a groundbreaking theory proposed by the British physicist Ernest Rutherford in 1911. This model provided a new understanding of the structure of the atom, moving away from the previously accepted plum pudding model.
Shell: The shell of an atom refers to the discrete energy levels or orbitals that electrons occupy around the nucleus. These shells represent the different possible energy states that electrons can have within an atom's structure.
Thomson: J.J. Thomson was a physicist who discovered the electron and proposed the 'plum pudding' model of the atom. His work laid the foundation for understanding atomic structure and electron behavior in atoms.
Valence Electrons: Valence electrons are the outermost electrons of an atom that participate in chemical bonding. They are the electrons that determine the chemical properties and reactivity of an element.