The atoms around you have existed for billions of years -- and most originated in the flaming, gaseous core of a star. Dennis Wildfogel tells the captivating tale of these atoms' long journeys from the Big Bang to the molecules they form today.
Everything in our universe has mass — from the smallest atom to the largest star. But the amount of mass has remained constant throughout existence even during the birth and death of stars, planets and you. How can the universe grow while maintaining its mass? Todd Ramsey answers that question by unravelling the law of conservation of mass.
A molecule is nearly all empty space, apart from the extremely dense nuclei of its atoms and the clouds of electrons that bond them together. When that molecule forms, it arranges itself to maximize attraction of opposite charges and minimize repulsion of unlike. George Zaidan and Charles Morton shape our image of molecules.
How elements relate to atoms. The basics of how protons, electrons and neutrons make up an atom.
More from The Khan Academy.
"Just how small are atoms? And what's inside them? The answers turn out to be astounding, even for those who think they know. This fast-paced animation uses spectacular metaphors (imagine a blueberry the size of a football stadium!) to give a visceral sense of the building blocks that make our world." View the complete lesson at TED-Ed.
"Atoms can (and do) bond constantly; it's how they form molecules. Sometimes, in an atomic tug-of-war, one atom pulls electrons from another, forming an ionic bond. Atoms can also play nicely and share electrons in a covalent bond. From simple oxygen to complex human chromosome 13, George Zaidan and Charles Morton break down the humble chemical bond." View the complete lesson at TED-Ed.
"The tiny atoms that make up our world are made up of even tinier protons, neutrons and electrons. Though the number of protons determines an atom's identity, it’s the electrons -- specifically, their exact location outside the nucleus -- that particularly perplex scientists. George Zaidan and Charles Morton show how to make an educated guess of where those itty-bitty freewheeling electrons might be." View the complete lesson at TED-Ed.
A lot of ionic compounds dissolve in water, dissociating into individual ions. But when two ions find each other that form an insoluble compound, they suddenly fall out of solution in what's called a precipitation reaction. In this episode of Crash Course Chemistry, we learn about precipitation, precipitates, anions, cations, and how to describe and discuss ionic reactions.