Atomic Radius @DeBaccoUniversity

Atomic Radius @DeBaccoUniversity

Uploaded August 2025 | Updated September 2026, 1 week ago

Atomic Radius

Dr. DeBacco

Atomic Radius
Atomic Radius- The size of an atom, typically measured as the distance from the nucleus to the outermost electron shell.

Atomic Radius: Across a Period
Across a Period (Left to Right): Decreases
The increasing nuclear charge (more protons) pulls electrons closer to the nucleus, while the number of electron shells remains constant.
Example: Lithium (Li) has a larger radius than fluorine (F) in Period 2.
Atomic Radius: Down a Group (or Family)
Down a Group or Family: Increases
The additional electron shells are added, increasing the distance between the nucleus and outer electrons, despite a higher nuclear charge.
Example: Cesium (Cs) has a larger radius than lithium (Li) in Group 1.

Link to Lecture Slides: drive.google.com/file/d/1j4WxVX0NuSb5PXP3A165ftCiXNUC2lWl/view?usp=drive_link

*Due to the description character limit the full work cited for "Atomic Radius" can be viewed at... docs.google.com/document/d/1EKTa3AU6w996mxpe7XECr8ybJt_lrdvJ/edit?usp=drive_link&ouid=104237452697237972847&rtpof=true&sd=true

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$Overview of the Main Components of an Atom Overview of the Main Components of an Atom Dr. DeBacco Main Components of an Atom Protons Neutrons Electrons The Proton A proton is a subatomic particle found in the nucleus of an atom. Charge: Protons carry a positive electric charge, equal in magnitude but opposite to the negative charge of an electron Mass: A proton has a mass of about 1.6726 × 10⁻²⁷ kg, roughly 1,836 times the mass of an electron but slightly less than that of a neutron. Location: Protons reside in the atomic nucleus, surrounded by a cloud of electrons orbiting at a distance. Proton Composition Composition: Protons are not fundamental particles but are made up of smaller fundamental particles called quarks. Specifically, a proton consists of two up quarks held together by the strong nuclear force mediated by gluons. The two quarks each with a charge of +2/3 and one down quark with a charge of -1/3. This gives the proton its net positive charge (+1). Role of The Proton Role in the Atom: Protons, along with neutrons, form the nucleus of an atom. The number of protons in an atom’s nucleus determines the atomic number, which defines the element 1 proton = hydrogen 6 protons = carbon The Electron An electron is a subatomic particle that orbits the nucleus of an atom. Charge: Electrons carry a negative electric charge, equal in magnitude but opposite to the positive charge of a proton. Mass: An electron has a mass of about 9.109 × 10⁻³¹ kg, approximately 1/1,836 the mass of a proton or neutron, making it extremely light. Location: Electrons exist in orbitals outside the nucleus, at varying energy levels. Electron Composition Composition: Electrons are considered fundamental particles, meaning they are not made up of smaller constituents Role of the Electron Role in the Atom: Electrons occupy regions around the nucleus called orbitals, forming an electron cloud. The number and arrangement of electrons determine an atom’s chemical properties, such as its reactivity and bonding behavior. The Neutron A neutron is a subatomic particle found in the nucleus of an atom. Charge: Neutrons are electrically neutral, carrying no electric charge (0 elementary charge). Mass: A neutron has a mass slightly greater than that of a proton but much greater than an electron’s mass (approximately 1,839 times heavier). Location: Neutrons reside in the atomic nucleus, alongside protons, at the core of the atom. Neutron Composition Composition: Neutrons are not fundamental particles but are composite, made up of smaller fundamental particles called quarks. Specifically, a neutron consists of one up quark and two down quarks held together by the strong nuclear force mediated by gluons. One Up quark with a charge of +2/3), and two down quarks each with a charge of -1/3) The charges of the quarks cancel out, resulting in the neutron’s neutrality. Role of the Neutron Role in the Atom: Neutrons, along with protons, form the nucleus of an atom. The number of neutrons determines the isotope of an element Ex. carbon-12 has 6 neutrons, carbon-14 has 8 Neutrons contribute to the nucleus’s mass and stability, helping to counterbalance the repulsive electromagnetic forces between positively charged protons. Quarks- Combine to Form Protons and Neutrons A quark is a fundamental subatomic particle that forms the building blocks of protons, neutrons, and other particles. Quarks- Charge and Mass Charge: Quarks carry fractional electric charges, either +2/3 or -1/3 of the elementary charge (approximately 1.602 × 10⁻¹⁹ coulombs). Up quark: +2/3 charge Down quark: -1/3 charge Other types (charm, strange, top, bottom) also have fractional charges. Mass: Quarks have extremely small masses, but their exact masses are complex to define due to quantum effects. Quarks Composition Composition: Quarks are fundamental particles in the Standard Model of particle physics, meaning they are not made of smaller constituents. They combine to form composite particles like… Protons (two up quarks, one down quark) Neutrons (one up quark, two down quarks) Role of the Quarks Role in the Atom: Quarks are not directly found in atoms but are the constituents of protons and neutrons, which form the atomic nucleus. Leptons A lepton is a fundamental subatomic particle belonging to a family distinct from quarks. Location: Electrons exist in orbitals around the atomic nucleus. Other leptons, like muons, taus, and neutrinos, are typically produced in high-energy processes (ex. cosmic rays, particle accelerators, or nuclear reactions) and are not part of stable atoms. Link to Lecture Slides: https://drive.google.com/file/d/16U_qxTVaQs1QUWWNzrvvHghXj57bQDl3/view?usp=drive_link *Due to the description character limit the full work cited for Overview of the Main Components of an Atom can be viewed at... https://docs.google.com/document/d/1WzSw2gX8MVf5r-OF3MvwqaGEQxK8xlu_/edit?usp=drive_link&ouid=104237452697237972847&rtpof=true&sd=true$

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Atomic Radius