Grade 9 Chemistry Lesson 10 - Ionic Compounds, Part 1 - Free Educational videos for Students in K-12

Grade 9 Chemistry Lesson 10 - Ionic Compounds, Part 1 - By Lumos Learning

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00:00	Hey , everybody , this is Mr Lee Han teaches
00:02	you stuff . Grade nine chemistry . Less than 10
00:05	ionic compounds . All right , so we're gonna start
00:09	off by looking at compounds in general before we get
00:12	into ionic compounds specifically . So compounds are pure substances
00:17	that are made up of two or more elements that
00:19	are chemically combined . Now it's important to note that
00:23	the properties of these compounds are not the same as
00:27	the elements that make them up . For example ,
00:32	uh , sodium chloride or table salt is very different
00:37	from sodium by itself or chlorine by itself . So
00:41	sodium by itself is a alkali metal , and it
00:46	will catch on fire if you put it in water
00:49	. It's extremely reactive . Chlorine is a green gas
00:56	, and it was used in World War one to
00:58	poison and kill soldiers . So when you put these
01:02	two elements together , they form sodium chloride or table
01:07	salt , which is fairly harmless except for my blood
01:11	pressure . But you can see that the compound has
01:15	wildly different characteristics , chemical characteristics or properties than the
01:20	elements that make it up . Now , in two
01:24	compounds have different amounts of the same elements . They
01:27	will have different properties For example , H 20 is
01:32	water . It's got one oxygen and two hydrogen .
01:36	H 202 is hydrogen peroxide . This has to oxygen
01:41	and two hydrogen . Now , hydrogen peroxide is used
01:45	to be used a lot as a disinfectant on cuts
01:48	, so it would basically kill anything around it .
01:52	And in highly concentrated doses , if you drink it
01:56	, it can be extremely dangerous and possibly even fatal
01:59	. Which reminds me of a joke . So two
02:02	people walk into a very literal bar . They go
02:05	up to the bartender and one says , Oh ,
02:06	I'd like a glass of H 20 and he has
02:10	it and he is refreshed and the other one says
02:12	, Oh , I'd like a glass of H 202
02:15	and he drinks it and he dies . Good joke
02:20	. Alright . Now ionic compounds ionic compounds are composed
02:24	of at least one metal and one non metal .
02:28	So something from the left side the metals combines with
02:32	something from the right side , the non metals ,
02:34	and it will give you an ionic compound . Now
02:38	, this is because the metals form positive ions had
02:42	non metals form negative ions , and they combined to
02:45	even each other out they have very high melting points
02:49	. They form crystals like salt , Uh , and
02:53	they dissolve in water like salt . Usually , if
02:56	you're thinking of properties of ionic compounds helps to think
02:59	of salt , which is an ionic compound . Because
03:01	, um , I'm sure you can easily remember that
03:04	so metals and non metals will combine to create ionic
03:07	compounds because all elements want to have full valence shells
03:12	just like the noble gases . So remember that oxygen
03:16	would need two more electrons to be like neon .
03:20	So when it gains those two , it becomes a
03:23	negatively charged ion , and it's going to get those
03:26	two electrons from some metal that's willing to give them
03:29	up . So metals and non metals combine to form
03:34	ionic compounds so that they can both have full valence
03:37	shells . Now what happens when lithium and oxygen combined
03:44	? Well , Lithium has one electron in its valence
03:46	shell , and it wants to get rid of that
03:48	electron . So there's the electron . It's trying to
03:51	get rid of . Oxygen , on the other hand
03:54	, has six electrons in its valence shell , and
03:57	it wants to gain two more , so oxygen has
04:00	to empty spaces right here . Since oxygen needs two
04:07	electrons and lithium only has one to give . Oxygen
04:10	is gonna need to steal electrons from two lithium atoms
04:13	, so we're gonna need to lithium for everyone oxygen
04:17	. So let's take those electrons away from the lithium
04:21	and we'll give them to the oxygen . And now
04:25	the two lithium is have a charge of one plus
04:28	, and the oxygen has a charge of two minus
04:30	, so they balance out the charges . So once
04:35	the atoms have become ions positively or negatively charged ,
04:39	they stick together because they have opposite charges . And
04:42	this is an ionic bond . So lithium and oxygen
04:47	combined to make lithium oxide or L . I .
04:50	20 Now you notice the two there . That subscript
04:55	means that there are two lithium atoms connected to the
04:58	one oxygen atom . So remember how oxygen needed to
05:01	take from two lithium seems to get balanced . Those
05:05	are the two lithium is there . That's how we
05:07	know that there's two of them . All right now
05:10	, I want to show you a fun way or
05:13	a quicker way to figure out what the chemical formula
05:15	would be for two ions forming a compound . So
05:19	the first thing you need to do is bring the
05:21	ion charges down as sub scripts for the other atoms
05:24	. But if the if the ion charges a one
05:27	like one plus or one minus , just ignore those
05:30	ones now if the two numbers are the same ,
05:33	so if the the metal and nonmetal both have the
05:36	same ion charge , you can just ignore them .
05:39	Ignore the numbers . If they're different , you got
05:42	to keep them . So here's what I'm talking about
05:45	. Magnesium has a charge , and I on charge
05:47	of two plus . It's up in the top right
05:49	there , and flooring has a charge of one minus
05:54	. So we've got our magnesium and our floor in
05:57	here . What we do is we bring the EI
06:01	on charges down as sub scripts for the other atoms
06:04	so that that one goes down to the magnesium and
06:07	the two goes down to the flooring and we end
06:10	up with MGF two . So remember that one we
06:13	don't put that in . We ignore it , but
06:16	the two stays there now . If we were doing
06:19	magnesium and oxygen , you'll notice that their charges are
06:22	the same , so their charges already balance out .
06:26	So when we cross those down , we just get
06:28	rid of them , and it becomes m g O
06:31	. Because they are the same , so we can
06:33	just ignore them . All right , we'll do a
06:36	couple more examples if lithium combines with nitrogen . Um
06:42	, we cross these down , okay ? And we're
06:45	going to have l i three n . So there's
06:48	going to be three nitrogen or three lithium for everyone
06:51	. Nitrogen . And then we have . But really
06:55	I'm in nitrogen . And that two goes down to
06:59	the nitrogen , the three goes down to the beryllium
07:02	, and now we have B E three and two
07:06	. So there's three beryllium and two nitrogen in each
07:10	molecule of that compound . Okay , so this is
07:14	a fairly easy little trick to figure out what the
07:19	chemical formula is going to be for an ionic compound
07:22	naming ionic compounds . So the first thing you need
07:25	to do is put them in the right order .
07:28	So the metal has to be first and the non
07:30	metal is second . And then you change the ending
07:34	of the non metal to ID . So , for
07:38	example , if you have magnesium and florian , that
07:43	becomes magnesium fluoride . So I changed the end of
07:46	flooring to fluoride . Magnesium oxygen is magnesium . oxide
07:55	, and then we have sodium and chlorine . They
07:58	come together to make sodium chloride and aluminum , and
08:03	sulfur becomes aluminum sulfide . So that's how we name
08:08	Ionic compounds . Metal first nonmetal second . And don't
08:12	forget to change the end to ID . Now you
08:14	can also figure out the chemical formulas from the name
08:17	of the compound . So on a test , you
08:20	might be asked what is the chemical formula for magnesium
08:23	sulfide ? And to figure this out , it's a
08:26	good idea to have the periodic table around to figure
08:29	out both what the symbols are and what the Ionic
08:31	charges would be for magnesium and sulfur . So we
08:36	find that magnesium is M . G . It's got
08:38	a charge of two plus and sulfur his s and
08:42	it has a charge of two minus . You'll notice
08:44	that those twos are the same . So we ignore
08:47	them , and we end up with MGs as the
08:50	formula . Next , we have beryllium falsified . So
08:56	beryllium has a charge of two . Plus phosphorus has
08:59	a charge of three minus . So when we cross
09:02	those down , we end up with a chemical formula
09:04	of B E three p two . Next , we
09:09	have aluminum chloride , aluminum has a charge of three
09:13	plus and chlorine has a charge of one minus .
09:16	So when we cross those down , we get a
09:18	l . C . L three . So there's three
09:22	chlorine atoms for everyone . Aluminum atom in that molecule
09:27	in that ionic compound and lithium chloride . One last
09:34	example . Lithium has a charge of one plus chlorine
09:38	has a charge of one minus . So we ignore
09:40	those , and we end up with L . I
09:42	. C . L . So that's it for this
09:44	video tune into the next video , where we look
09:47	at Ionic compounds , part two compounds with multi Valent
09:51	elements and Polly Atomic ions .

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