Grade 9 Chemistry Lesson 12 Molecular Compounds - Free Educational videos for Students in K-12

Grade 9 Chemistry Lesson 12 Molecular Compounds - By Lumos Learning

Transcript


00:00	Hey there . Welcome to Mr Lee Han teaches you
00:02	stuff . This is great . Nine chemistry . Less
00:04	than 12 molecular compounds . So a molecular compound is
00:10	when you have to non metals joint . Um ,
00:14	And when they joined , they don't steal the electrons
00:16	, like ionic compounds do . So they don't create
00:20	, like , positive and negative ions . Um ,
00:23	instead , they share the electrons . That's nice .
00:27	Um , and they share these electrons for the same
00:29	reasons that ionic compounds steal them . And that's to
00:33	fill up their valence shells so they can be like
00:36	the noble gases over on the far right of the
00:38	table that have full valence shells . So water is
00:43	an example of a molecular compound . I'm sure we're
00:46	all familiar with water or H 20 Um , Now
00:50	H 20 has to hide regions . That's the H
00:53	two and one oxygen atom . Now the oxygen needs
00:59	two more electrons to fill its valence shell , so
01:02	that's oxygen in the middle . And it has six
01:05	electrons in its valence shell , but it needs eight
01:08	to have a full valence shell like neon the hydrogen
01:13	. They need one electron to fill their valence shells
01:16	because then we'll have to just like helium , so
01:20	to fill up the valence shells of the hydrogen and
01:24	the oxygen . What happens is they link up and
01:27	they share electrons . So the two unpaid electrons that
01:32	oxygen had are now shared with the hydrogen atoms ,
01:37	so the hydrogen now have to oxygen now has eight
01:40	in its shell , and everybody's happy Now . Molecular
01:44	compounds can be solids , liquids or gases at room
01:48	temperature , so it's not really set in stone that
01:50	they're all solids . They're all liquids or anything like
01:52	that . They can be a variety of things ,
01:56	Um , and they have relatively low boiling points .
01:59	So water , for example , has a boiling point
02:02	of 100 degrees Celsius . If we compare that to
02:06	an Ionic compound like salt , salt has a boiling
02:10	point of 1413 degrees Celsius , so water seems relatively
02:16	low by comparison , Um , and they usually do
02:19	not conduct electricity well , so things like rubber or
02:24	plastic that goes around wires . Those insulate us from
02:29	the wires , right ? If you touch a wire
02:31	that's got a rubber coating on it or a plastic
02:34	coating on it , you don't get electrocuted . And
02:37	that's because that plastic is a molecular compound that does
02:40	not conduct electricity well , combining capacities . The combining
02:45	capacity of an element refers to how many bonds it
02:48	can form with other atoms . So how many other
02:51	atoms can it be linked to ? In general ,
02:55	the combining capacity will be the same as the Ionic
02:58	charge that that element can form . So if we're
03:01	just looking over here at the non metals , we'll
03:03	start off with Boron . Warren conformed . Three bonds
03:08	. Carbon , although it can't form an ion ,
03:10	will form bonds , and it can form four bonds
03:15	. Nitrogen can form three oxygen to Florian one ,
03:20	and then helium can form nothing . And that's the
03:22	same for the whole columns there , so everything under
03:26	helium will form zero . Everything under flooring will form
03:29	one bond , etcetera . Now , the reason why
03:34	the whole column will form the same number of bonds
03:38	is because the combining capacity will be the same as
03:41	the number of unpaid electrons in the valence shell .
03:44	So we'll take a look at carbon so carbon can
03:48	form four bonds . Here here it's bonded to four
03:51	hydrogen . The reason why , if we look at
03:55	the board diagram for carbon is that carbon has four
04:01	unpaid electrons in its valence shell . That means it
04:05	has four empty spots where other atoms can join up
04:09	with the carbon . Okay , when we are naming
04:12	molecular compounds , we need to add prefixes to the
04:15	elements so that we know how many are in each
04:18	compound , and the reason we do this is because
04:21	they can combine in different combinations . So even if
04:24	you have the same two elements combining , they can
04:28	combine in different ways and you'll end up with different
04:30	chemicals . For example , carbon and oxygen just C
04:35	O is carbon monoxide . That's one chemical . But
04:39	then C 02 is carbon dioxide , a completely different
04:43	chemical with completely different chemical properties . So when we're
04:47	naming molecular compounds just like ionic compounds , we name
04:51	the two elements and then change the end of the
04:53	second one to ID . But unlike Ionic compounds ,
04:57	we need to add prefixes to the elements as well
05:01	. For example , n 20 If that was an
05:04	ionic compound , it would just be nitrogen oxide .
05:08	But these are both non metals , nitrogen and oxygen
05:12	, so we know this is a molecular compound ,
05:14	so we need to add prefixes , and it is
05:17	die nitrogen monoxide So let's just quickly rattle through the
05:22	different prefixes that we can put into molecular compound names
05:27	. Mono means one di means two tri means three
05:33	Tetra means for , and these four here will be
05:37	the most common ones that you will run into .
05:38	But we'll go through the 1st 10 possible ones ,
05:42	just in case you need them . So Pente means
05:45	five Hex is six . Help to seven . Octa
05:50	is eight , Nana is nine and deca is 10
05:55	. So those are all the possible prefixes that you
05:58	can find in molecular compounds . So when we're naming
06:02	molecular compounds , if there's only one of the first
06:05	element , then we don't give it a prefix .
06:08	So there's no mono . For example , CO two
06:12	is carbon dioxide . We don't call it mano carbon
06:15	dioxide , So if there's a name of a molecular
06:19	compound , it just starts off with an element just
06:23	like carbon dioxide . We just assume that that means
06:26	that its motto Carbon dioxide . But we don't write
06:29	mono , so let's go through a few examples where
06:32	we name molecular compounds . Uh , this first one
06:36	is just carbon and oxygen , one of each ,
06:38	so it's going to be carbon monoxide for the second
06:43	one . We've got one carbon and four Florina .
06:47	The prefix for four is Tetra . So this one's
06:50	gonna be carbon tetrachloride . Then we have two nitrogen
06:56	and four oxygen . So too , is die and
07:00	forest tetra . So we end up with Di nitrogen
07:04	tetroxide and then our last example . Here we have
07:08	one phosphorus and three chlorine and that ends up being
07:14	phosphorus . Try chloride . All right . Now ,
07:19	if we're going the other way , we want to
07:20	figure out what the chemical formula is . Uh ,
07:22	the number of atoms is already provided in the name
07:25	, so it's pretty straightforward . Just list the elements
07:28	symbols in order and include the necessary sub scripts .
07:32	So , for example , di hydrogen dioxide means there's
07:36	two of each , so you put a church to
07:38	go to . So what is the chemical formula for
07:42	di hydrogen monoxide ? Well , the dye means there's
07:46	two hydrogen and then there's one oxygen . So that's
07:49	going to be a church to , oh , better
07:51	known as water . Then we have carbon tetra hydride
07:56	, so we know there's gonna be one carbon tetra
07:59	means force was going to be four hydrogen , so
08:02	we get ch four , also known as methane then
08:07	we have di phosphorus pent oxide . So die means
08:11	there's two . Penta means there's five . So we
08:15	get P 205 and then our last example . Here
08:19	we have dying nitrogen hexafluoride . The dye means there's
08:24	two , and Hexham means there's six , so we
08:27	get n two cl six . All right , so
08:30	that's it for the Grade nine chemistry unit . I
08:33	hope you enjoyed watching these videos almost as much as
08:36	I like making them .

Summarizer

DESCRIPTION:

OVERVIEW:

Grade 9 Chemistry Lesson 12 Molecular Compounds is a free educational video by Lumos Learning.

This page not only allows students and teachers view Grade 9 Chemistry Lesson 12 Molecular Compounds videos but also find engaging Sample Questions, Apps, Pins, Worksheets, Books related to the following topics.