How atoms bond - George Zaidan and Charles Morton
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0:07 - 0:09Most atoms don't ride solo,
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0:09 - 0:12instead they bond with other atoms.
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0:12 - 0:14And bonds can form between atoms
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0:14 - 0:15of the same element
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0:15 - 0:17or atoms of different elements.
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0:17 - 0:20You've probably imagined bonding as a tug of war.
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0:20 - 0:22If one atom is really strong,
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0:22 - 0:24it can pull one or more electrons
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0:24 - 0:26off another atom.
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0:26 - 0:29Then you end up with one negatively charged ion
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0:29 - 0:31and one positively charged ion.
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0:31 - 0:34And the attraction between these opposite charges
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0:34 - 0:36is called an ionic bond.
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0:36 - 0:37This is the kind of sharing
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0:37 - 0:40where you just give away your toy to someone else
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0:40 - 0:42and then never get it back.
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0:43 - 0:45Table salt, sodium chloride,
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0:45 - 0:48is held together by ionic bonds.
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0:48 - 0:50Every atom of sodium gives up one electron
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0:50 - 0:52to every atom of chlorine,
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0:52 - 0:53ions are formed,
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0:53 - 0:55and those ions arrange themselves
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0:55 - 0:58in a 3D grid called a lattice,
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0:58 - 0:59in which every sodium ion
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0:59 - 1:02is bonded to six chloride ions,
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1:02 - 1:03and every chloride ion is bonded
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1:03 - 1:06to six sodium ions.
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1:06 - 1:07The chlorine atoms never give
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1:07 - 1:10the sodium atoms their electrons back.
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1:11 - 1:14Now, these transactions aren't always so cut-and-dried.
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1:14 - 1:17If one atom doesn't completely overwhelm the other,
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1:17 - 1:19they can actually share each other's electrons.
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1:19 - 1:21This is like a pot luck
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1:21 - 1:23where you and a friend each bring a dish
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1:23 - 1:26and then both of you share both dishes.
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1:26 - 1:27Each atom is attracted to the shared electrons
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1:27 - 1:29in between them,
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1:29 - 1:32and this attraction is called a covalent bond.
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1:32 - 1:34The proteins and DNA in our bodies,
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1:34 - 1:35for example,
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1:35 - 1:38are held together largely by these covalent bonds.
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1:38 - 1:39Some atoms can covalently bond
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1:39 - 1:41with just one other atom,
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1:41 - 1:43others with many more.
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1:43 - 1:44The number of other atoms
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1:44 - 1:46one atom can bond with
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1:46 - 1:49depends on how its electrons are arranged.
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1:49 - 1:52So, how are electrons arranged?
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1:52 - 1:54Every atom of a pure, unbonded element
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1:54 - 1:55is electrically neutral
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1:55 - 1:57because it contains the same number
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1:57 - 1:58of protons in the nucleus
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1:58 - 2:01as it does electrons around the nucleus.
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2:01 - 2:04And not all of those electrons are available for bonding.
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2:04 - 2:06Only the outermost electrons,
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2:06 - 2:09the ones in orbitals furthest from the nucleus,
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2:09 - 2:10the ones with the most energy,
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2:10 - 2:13only those participate in bonding.
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2:13 - 2:16By the way, this applies to ionic bonding too.
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2:16 - 2:17Remember sodium chloride?
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2:17 - 2:19Well, the electron that sodium loses
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2:19 - 2:22is the one furthest from its nucleus,
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2:22 - 2:23and the orbital that electron occupies
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2:23 - 2:25when it goes over to chlorine
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2:25 - 2:28is also the one furthest from its nucleus.
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2:28 - 2:30But back to covalent bonding.
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2:30 - 2:32Carbon has four electrons
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2:32 - 2:33that are free to bond,
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2:33 - 2:34nitrogen has three,
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2:34 - 2:35oxygen two.
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2:35 - 2:37So, carbon is likely to form four bonds,
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2:37 - 2:38nitrogen three,
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2:38 - 2:40and oxygen two.
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2:40 - 2:41Hydrogen only has one electron,
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2:41 - 2:43so it can only form one bond.
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2:43 - 2:45In some special cases,
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2:45 - 2:46atoms can form more bonds
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2:46 - 2:48than you'd expect,
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2:48 - 2:50but they better have a really good reason to do so,
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2:50 - 2:52or things tend to fly apart.
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2:52 - 2:53Groups of atoms
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2:53 - 2:55that share electrons covalently with each other
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2:55 - 2:57are called molecules.
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2:58 - 2:59They can be small.
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2:59 - 3:01For example, every molecule of oxygen gas
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3:01 - 3:03is made up of just two oxygen atoms
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3:03 - 3:05bonded to each other.
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3:05 - 3:06Or they could be really, really big.
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3:06 - 3:09Human chromosome 13 is just two molecules,
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3:09 - 3:13but each one has over 37 billion atoms.
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3:13 - 3:14And this neighborhood,
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3:14 - 3:15this city of atoms,
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3:15 - 3:18is held together by the humble chemical bond.
- Title:
- How atoms bond - George Zaidan and Charles Morton
- Description:
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View full lesson: http://ed.ted.com/lessons/how-atoms-bond-george-zaidan-and-charles-morton
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.
Lesson by George Zaidan and Charles Morton, animation by Bevan Lynch.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 03:34
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