Elements and atomic number | Atoms, isotopes, and ions | High school chemistry | Khan Academy

Summary

This Khan Academy video dives into the basics of elements and atomic numbers, highlighting that all matter in the universe is composed of atoms. Elements, each distinct in their properties, are defined by their number of protons, known as the atomic number. The video explains that these atomic numbers help us understand the number of electrons in neutral atoms, as well. The organization of elements is showcased through the periodic table, which lists them by increasing atomic number and groups them by similar properties. This video also delves into the significance of chemical symbols and atomic masses, emphasizing how knowing one property of an element can help identify others using the periodic table, through engaging examples.

Highlights

• All matter in the universe is made of atoms, with elements being different types of atoms. 🌌
• Each element is distinct, identified by its atomic number—the number of protons it contains. 🔍
• The periodic table not only orders elements by atomic number but also groups them by similar properties. 🧩
• Chemical symbols, derived from English or Latin, are the shorthand of chemistry. ✏️
• Understanding atomic numbers and electron configurations helps in explaining an element’s chemical behavior. 🧪

Key Takeaways

• Every element is identified by its unique atomic number, which is the count of protons in its atoms. 🔢
• The periodic table is a systematic arrangement of elements by atomic number, revealing patterns in properties. 📊
• Elements are represented by chemical symbols, often based on English or Latin names, making chemistry universally understandable. 🌍
• Equal numbers of protons and electrons balance out to keep atoms neutral. ⚖️
• Knowing an element's atomic number, symbol, or name can reveal additional details through the periodic table. 🤓

Overview

In this captivating Khan Academy presentation, viewers are introduced to the fundamental concept that everything in the universe is composed of elements, each a unique type of atom. It’s fascinating to see how each element, whether common like oxygen or exotic like xenon, is defined by its atomic number, representing the count of protons in its atom’s nucleus.

The video further elaborates on the elegant design of the periodic table, which neatly organizes elements according to their atomic numbers from left to right and top to bottom. Not just a bland list of atomic facts, the periodic table also clusters elements into columns based on shared physical and chemical traits, offering deeper insights into their interactions.

Adding a layer of intrigue, the video unwraps the story behind chemical symbols—oftentimes rooted in Latin or English—and how they serve as a universal language for scientists across the globe. By navigating through practical examples, viewers can easily pick up how to deduce properties such as atomic numbers and electron configurations, making each visit to the periodic table a bit like scientific detective work.

Chapters

• 00:00 - 00:30: Introduction to Elements The chapter titled 'Introduction to Elements' explains that everything in the universe is made up of atoms, but not all atoms are identical. These different types of atoms are called elements, and they each possess unique physical and chemical properties. Some elements, like oxygen and carbon, are well-known, while others, such as bismuth, xenon, and osmium, might be less familiar.
• 00:30 - 01:00: Atomic Number The chapter 'Atomic Number' explains that the atomic number of an element is determined by the number of protons in its atoms. This number, represented by the symbol Z, is unique to each element. For instance, helium, with an atomic number of 2, has two protons in each of its atoms, while iron has an atomic number of 26, indicating 26 protons per atom.
• 01:00 - 01:30: Atomic Number and Electrons The chapter explains the relationship between an element's atomic number and the number of electrons in a neutral atom. It emphasizes that a neutral atom must have equal numbers of protons and electrons to cancel out opposite charges and maintain neutrality. Examples given include helium, which has two electrons, and iron, which has 26 electrons.
• 01:30 - 02:00: Periodic Table Organization The chapter explains the organization of the periodic table based on atomic numbers and properties. It describes how elements are listed in order of increasing atomic number from left to right and top to bottom. Furthermore, it explains that elements are grouped into columns, or 'families,' where elements in the same column exhibit similar physical and chemical properties.
• 02:00 - 02:30: Chemical Symbols The chapter titled 'Chemical Symbols' explores the concept of chemical symbols, which are unique one or two-letter abbreviations displayed under an element's atomic number on the periodic table. It explains that many chemical symbols derive from the English names of elements, like H for Hydrogen and Al for Aluminum. However, some symbols are based on Latin names, such as Pb for Lead, which originates from its Latin name.
• 02:30 - 03:00: Understanding the Periodic Table The chapter focuses on understanding the layout and the information contained in the periodic table, particularly how the chemical symbols are formatted. It explains that chemical symbols with two letters will have the second letter in lowercase. The chapter uses the example of the element nitrogen to illustrate how information is presented in each element's box on the periodic table, noting the importance of the atomic number, which equals the number of protons in each atom of the element.
• 03:00 - 04:00: Examples of Using the Periodic Table The chapter covers the basic layout and usage of the periodic table, specifically focusing on nitrogen as an example. It explains the significance of the atomic number, chemical symbol, and atomic mass, all of which can typically be found in an element's box on the table. The chapter hints that knowing any one of these details can enable you to gather more information about an element using the periodic table.
• 04:00 - 05:00: Conclusion The chapter 'Conclusion' provides practical examples regarding the use of the periodic table to identify elements. It illustrates how to determine the atomic number and chemical symbol of elements such as phosphorus, which has an atomic number of 15 and is represented by the symbol 'P'. Additionally, the chapter poses a challenge by giving a chemical symbol, 'HG', to identify its corresponding element, encouraging applied learning of the periodic table.

Elements and atomic number | Atoms, isotopes, and ions | High school chemistry | Khan Academy Transcription

• 00:00 - 00:30 we know that everything in the universe is composed of atoms but not all atoms are the same there are many different types of atoms called elements each with a unique set of physical and chemical properties many elements are probably familiar to you oxygen and carbon for example are elements and so is gold others may be less familiar such as bismuth Xenon and osmium
• 00:30 - 01:00 a particular element is identified by the number of protons and its atoms and the number of protons in the nucleus of an atom is its atomic number represented by the symbol Z for example helium has an atomic number of two that means that every helium atom has two protons and here's another example iron its atomic number is 26 so every iron
• 01:00 - 01:30 atom has 26 protons an element's atomic number can also tell us the number of electrons in a neutral atom of an element remember equal and opposite charges cancel each other out so to be neutral an atom must have an equal number of protons which have a charge of one plus and electrons which have a charge of one minus this means that our helium atom must have two electrons and our iron atom must have 26
• 01:30 - 02:00 electrons all of the known elements are organized according to their atomic numbers in the periodic table the periodic table lists the elements in order of increasing atomic number as you go from left to right and from top to bottom the elements are further organized into columns based on their properties elements in the same column tend to have similar physical and chemical properties every element is represented by a
• 02:00 - 02:30 chemical symbol a unique one or two letter abbreviation that appears below the element's atomic number on the periodic table many chemical symbols are based on the English name for an element for example the symbol for hydrogen is H and the symbol for aluminum is Al but some chemical symbols are based on the Latin name for the element for example the symbol for lead is PB which actually comes from its Latin name
• 02:30 - 03:00 plumbum notice that whenever the chemical symbol for an element has two letters the second letter is written in lower case all of this information is contained inside of each element's box on the periodic table for example here's the box for the element nitrogen at the top of the box is nitrogen's atomic number which is seven remember that this is equal to the number of protons in each atom of nitrogen as well as the number
• 03:00 - 03:30 of electrons below that is nitrogen's chemical symbol n followed by its name often you'll also see another number listed at the bottom of an element's box which has to do with atomic mass we'll cover details about this in another video what's neat about having all of this information in one place is that if we know one detail about an element either its atomic number chemical symbol or name we can often use the periodic table
• 03:30 - 04:00 to find out the other details let's take a look at a few examples say we have the element phosphorus what is its atomic number and chemical symbol looking through the periodic table we can find phosphorus and see that its atomic number is 15 and its chemical symbol is p let's do another example say we know the chemical symbol HG what is this
• 04:00 - 04:30 element's name and how many protons does it have here is the symbol HG on the periodic table its name is Mercury and its atomic number is 80. so it has 80 protons let's review the universe is made up of different types of atoms called elements and these elements are organized by atomic number in the periodic table so the next time that you stare up at the Starry Sky you know that everything
• 04:30 - 05:00 out there is made up of elements