Elements and atoms | Atoms, compounds, and ions | Chemistry | Khan Academy

HUMANS HAVE KNOWN FOR THOUSANDS OF YEARS, JUST BY LOOKING AT THE ENVIRONMENT THAT SURROUNDS US, THAT THERE ARE DIFFERENT SUBSTANCES. THESE DIFFERENT SUBSTANCES GENERALLY HAVE DIFFERENT PROPERTIES, NOT ONLY DO THEY HAVE DIFFERENT PROPERTIES, THEY CAN REFLECT LIGHT IN A CERTAIN WAY, OR NOT REFLECT LIGHT. OR MAYBE A CERTAIN COLOR, OR HAS A CERTAIN TEMPERATURE, IT COULD BE A LIQUID, GAS OR SOLID. BUT WE ALSO OBSERVE HOW THEY REACT WITH EACH OTHER UNDER CERTAIN CIRCUMSTANCES AND HERE I LEAVE YOU PHOTOS OF SOME OF THESE SUBSTANCES. IT'S CARBON, IT'S IN ITS GRAPHITE FORM IT'S LEAD, IT'S GOLD AND I DRAWN ALL OF THIS AND I TOOK PHOTOS I GOT IT ALL FROM THIS WEBSITE HERE EVERYTHING IS IN ITS SOLID FORM BUT WE ALSO KNOW THAT IT LOOKS LIKE THERE ARE CERTAIN TYPES OF THE AIR THERE ARE CERTAIN TYPES OF THE AIR OF AIR PARTICLES AND DEPENDING ON WHICH THE AIR PARTICLES WHETHER CARBON, OXYGEN OR NITROGEN, THEY HAVE DIFFERENT PROPERTIES.

OR THERE ARE SOME OTHER SUBSTANCES THAT CAN BE LIQUIDS OR IF YOU MAKE THE TEMPERATURE HIGH ENOUGH ON THESE SUBSTANCES IF YOU MAKE THE TEMPERATURE HIGH ENOUGH ON GOLD OR LEAD YOU CAN GET A LIQUID. OR IF YOU LET THE CARBON BURN, IT GOES INTO THE GAS PHASE, IT IS RELEASED INTO THE ATMOSPHERE, ITS STRUCTURE BREAKS. SO ALL THESE THINGS WE AS HUMANS OBSERVED FOR THOUSANDS OF YEARS. BUT THIS LEADS TO A NATURAL QUESTION WHICH FIRST WAS A PHILOSOPHICAL QUESTION BUT NOW WE CAN ANSWER IT BETTER AND THE QUESTION IS, IF THIS CARBON IS CONTINUOUSLY BREAKED INTO SMALLER AND SMALLER PARTICLES IF THERE IS A SMALLER PART THE SMALLEST UNIT OF THIS PART, OF THIS SUBSTANCE THAT STILL HAS THE PROPERTIES OF CARBON?

WHAT IF YOU COULD BREAK THAT PIECE MORE WOULD YOU LOSE THE PROPERTIES OF THE CARBON? AND THE ANSWER IS: THERE IS. AND SO THAT WE HAVE OUR TERMINOLOGY CORRECT, WE CALL THESE DIFFERENT SUBSTANCES, PURE SUBSTANCES THAT HAVE THESE SPECIFIC PROPERTIES AT A CERTAIN TEMPERATURE AND REACT IN A CERTAIN WAY, WE CALL THEM ELEMENTS. CARBON IS AN ELEMENT. LEAD IS AN ELEMENT. GOLD IS AN ELEMENT. YOU CAN SAY THAT WATER IS ALSO AN ELEMENT AND IN THE PAST PEOPLE REFERRED TO WATER AS AN ELEMENT BUT NOW WE KNOW THAT WATER IS MADE UP OF MORE BASIC ELEMENTS.

IT IS COMPOSED OF OXYGEN AND HYDROGEN AND ALL OUR ELEMENTS ARE LISTED HERE IN THE PERIODIC TABLE OF ELEMENTS C WHICH MEANS CARBON I AM ONLY GOING THROUGH THE ELEMENTS THAT ARE OF INTEREST TO MAN BUT IN TIME YOU WILL SURE BE PROFESSIONAL WITH ALL THESE ELEMENTS THIS IS OXYGEN . THIS IS NITROGEN. IT'S SILICONE. EN- Oh IT'S GOLD. IT IS LEAD AND THE MOST BASIC UNIT OF AN ELEMENT IS THE ATOM. SO IF YOU CONTINUOUSLY DECOMPLETE AN ELEMENT AND CONTINUALLY TAKE IN MORE AND SMALLER PARTICLES, YOU WILL FINALLY GET TO THE CARBON ATOM. DO THE SAME HERE, YOU WILL FINALLY END UP WITH THE GOLD ATOM.

IF YOU DID THE SAME THING HERE, YOU WOULD EVENTUALLY RECEIVE PARTS OF THIS LITTLE A.G.V. A WORD TOO SHORT FOR A BETTER: A PARTICLE YOU WILL CALL LEAD ATOM. AND YOU CAN'T BREAK IT DOWN FURTHER AND STILL CALL IT LEAD BECAUSE IT STILL HAS THE PROPERTIES OF LEAD AND JUST TO GIVE YOU AN IDEA, WHAT I'M REALLY BEING A LITTLE HARD TO UNDERSTAND IS THAT THE ATOMS ARE INCREDIBLY SMALL. REALLY INCREDIBLY SMALL SO BV., CARBON. MY HAIR IS ALSO COMPOSED OF CARBON FINALLY THE LARGEST PART OF ME IS COMPOSED OF CARBON FINALLY ALL LIVING THINGS ARE COMPOSED OF CARBON AND SO YES THEY TAKE ME THAT.

SO MY HAIR IS CARBON MY HAIR IS MOSTLY CARBON SO IF YOU TAKE MY HAIR HERE MY HAIR IS NOT YELLOW BUT IT IS A GOOD CONTEXT WITH THE BLACK. MY HAIR IS BLACK. BUT IF I HAD TO ILLUSTRATE IT YOU WOULD NOT BE ABLE TO SEE IT ON SCREEN. BUT IF YOU TAKE MY HAIR, THEN I ASK YOU HOW MANY CARBON ATOMS WIDE IS MY HAIR? So if you were to take a cross section of my hair, not the length, but the width of my hair, and say, how many carbon

atoms

is it wide?