Isotopes | Atoms, isotopes, and ions | High school chemistry | Khan Academy

Summary

Highlights

• The atomic number defines the element, while the neutron number varies in isotopes. 🔍
• Mass number is the sum of protons and neutrons in the nucleus. ⚖️
• Isotope notation helps in representing isotopes in a clear, concise manner. ✍️

Key Takeaways

• Isotopes are variants of elements with different neutron numbers. 🧪
• Mass number equals protons plus neutrons. 🔢
• Carbon-12 and Carbon-13 are examples of isotopes. 🌿
• Isotopes can be notated using different styles: X-A or positioned numbers alongside symbols. 📒

Overview

Chapters

• 00:00 - 00:30: Elements and Protons The chapter discusses how elements are defined by their atomic number, which is the number of protons in their atoms. For instance, every atom of potassium has 19 protons, while cobalt has 27. The chapter also introduces the concept of isotopes, explaining that atoms of the same element can have different numbers of neutrons, thus forming isotopes.
• 00:30 - 01:00: Isotopes and Mass Number Isotopes are atoms with the same number of protons but different numbers of neutrons, leading to different masses.
• 01:00 - 01:30: Isotope Notation This chapter covers how isotopes are represented in writing, explaining the notation used. X represents the chemical symbol, a is the mass number (the total of protons and neutrons), and Z is the atomic number (the number of protons). The chapter provides an example using carbon, which has an atomic number of six.
• 01:30 - 03:00: Carbon Isotopes Examples Carbon is primarily composed of two isotopes. The first isotope of carbon has six protons and six neutrons, giving it a mass number of 12. Its notation is represented using its chemical symbol C.
• 03:00 - 04:30: Summary and Recap This chapter explains the notation used for representing isotopes, specifically focusing on carbon isotopes with different numbers of neutrons. It details how the mass number is calculated by adding the number of protons and neutrons, and provides an example using carbon isotopes. The transcript describes the representation of the isotope with six protons and six neutrons, as well as the isotope with six protons and seven neutrons, highlighting the difference in mass numbers.

Isotopes | Atoms, isotopes, and ions | High school chemistry | Khan Academy Transcription

• 00:00 - 00:30 every element is defined by the number of protons in its atoms which is called its atomic number so for example every atom of potassium has 19 protons and every atom of cobalt has 27 protons but what about neutrons well an element doesn't always have the same number of neutrons in its atoms atoms of the same element with different numbers of neutrons are called isotopes because isotopes of an element have
• 00:30 - 01:00 different numbers of neutrons those Isotopes also have different masses remember most of the mass of an atom comes from the protons and neutrons in its nucleus in fact the sum of the number of protons and neutrons in an atom is called its mass number we can write this in the form of an equation as follows mass number equals the number of protons plus the number of neutrons next let's dive into isotope notation or
• 01:00 - 01:30 how we represent Isotopes in writing when describing different isotopes you'll often see this notation where X is the chemical symbol which is an abbreviation of the element's name a is the mass number the number of protons plus neutrons and Z is the atomic number the number of protons let's practice writing out the notation for different isotopes we'll start with carbon which has an atomic number of six
• 01:30 - 02:00 in nature carbon is mainly composed of two different isotopes one of these Isotopes has six neutrons and the other isotope has seven neutrons let's start with the isotope that has six protons and six neutrons with that information we know that the mass number must be 12 which is the sum of the protons and neutrons so the notation for this isotope of carbon would look like this we have the chemical symbol C with the
• 02:00 - 02:30 mass number 12 written at its top left and the atomic number six written at its bottom left but for the isotope with six protons and seven neutrons the mass number would be six plus seven or thirteen so the notation for the carbon isotope would be as follows here we have the chemical symbol C with the mass number 13 written at its top left and the atomic number six written
• 02:30 - 03:00 at its bottom left notice that the chemical symbol and atomic number share the same information the identity of the element and are the same for both isotopes but the mass number is different for each isotope depending on the number of neutrons another notation that is used for Isotopes is the chemical symbol or the element's name symbolized by X followed by a hyphen and the mass number symbolized by a so X hyphen a
• 03:00 - 03:30 let's return to our carbon Isotopes example for the carbon isotope that has six protons and six neutrons we write that as c hyphen 12 or carbon 12. for the carbon isotope with six protons and seven neutrons we write that as c hyphen 13 or carbon 13. let's wrap up this video with a quick recap we know that elements are defined
• 03:30 - 04:00 by the number of protons in their atoms but atoms of the same element can have different numbers of neutrons these are called isotopes because Isotopes have different numbers of neutrons they also have different Mass numbers which are the sum of the protons and neutrons in each Isotopes atom and Adam's mass number can be described by the equation mass number equals the number of protons plus the number of
• 04:00 - 04:30 neutrons and lastly we can describe Isotopes using a couple of different notations which are shown below