https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:atoms-isotopes-and-ions/x2613d8165d88df5e:atomic-structure/v/protons-neutrons-and-electrons-in-atoms 2025-11-01T06:31:04.963641538Z Protons, neutrons, and electrons in atoms Atoms are made up of three types of subatomic particles: protons, neutrons, and electrons. Protons and neutrons are found in the nucleus, the dense region at the center of an atom. Electrons are found outside the nucleus. Protons are positively charged and have a mass of about 1 u. Neutrons are neutral (have no charge) and also have a mass of about 1 u. Electrons are negatively charged and have a much smaller mass of about 0.0005 u. Wieteke Holthuijzen video https://cdn.kastatic.org/ka_thumbnails_cache/b0e49086-7776-4d8b-8b13-7afbfd62b856_1280_720_base.png Protons, neutrons, and electrons in atoms Atoms are made up of three types of subatomic particles: protons, neutrons, and electrons. Protons and neutrons are found in the nucleus, the dense region at the center of an atom. Electrons are found outside the nucleus. Protons are positively charged and have a mass of about 1 u. Neutrons are neutral (have no charge) and also have a mass of about 1 u. Electrons are negatively charged and have a much smaller mass of about 0.0005 u. https://cdn.kastatic.org/ka-youtube-converted/lz_gMkQr7YE.mp4/lz_gMkQr7YE.mp4 151 Structure of an atom https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:atoms-isotopes-and-ions/x2613d8165d88df5e:atomic-structure/v/elements-and-atomic-number 2025-12-03T14:30:51.007256483Z Elements and atomic number Atoms come in a variety of types, called elements, each with a unique set of physical and chemical properties. An element is defined by the number of protons in its atoms, known as its atomic number. The periodic table organizes the elements by atomic number and provides other key information about them such as their names and chemical symbols. Wieteke Holthuijzen video https://cdn.kastatic.org/ka_thumbnails_cache/f9b78e3a-4de0-46ed-a0cb-3e36d84fa21b_1280_720_base.png Elements and atomic number Atoms come in a variety of types, called elements, each with a unique set of physical and chemical properties. An element is defined by the number of protons in its atoms, known as its atomic number. The periodic table organizes the elements by atomic number and provides other key information about them such as their names and chemical symbols. https://cdn.kastatic.org/ka-youtube-converted/OQi8FwPSu5o.mp4/OQi8FwPSu5o.mp4 274 Structure of an atom https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:atoms-isotopes-and-ions/x2613d8165d88df5e:atomic-structure/e/understand-atomic-structure 2026-04-07T22:59:30.107127435Z Understand: atomic structure Check your understanding of atomic structure in this set of free practice questions. Megan Cohn exercise https://www.khanacademy.org/science/mh-grade-8-science/x0f256b8de9c7cf34:inside-the-atom/x0f256b8de9c7cf34:atomic-models/e/lo-3-1-constituents-of-atom-and-their-charge 2025-06-26T08:56:38.363651408Z Constituents of atom and their charge Let's solve some problems to better understand what is inside the atom and the charge of it's constituent particles. Aakash Bagga exercise https://www.khanacademy.org/science/mh-grade-8-science/x0f256b8de9c7cf34:inside-the-atom/x0f256b8de9c7cf34:atomic-number-and-mass-number/e/lo-2-3-atomic-number-and-mass-number 2025-08-05T18:56:35.058002345Z Atomic number and mass number Let's solve some problems to better understand atomic and mass numbers. Aakash Bagga exercise