bonding? POS Checklist: electrostatic Ionic Bonding Your Periodic Table Sep 16 2:27 PM Aug 19 11:54 AM Sep 17 10:13 AM Sep 3 3:45 PM

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1 Chemistry 20 Unit A Bonding Ionic Bonding and Your Periodic Table You will... POS Checklist: explain how an ic bond results from the simultaneous attract of oppositely charged s. define the terms valence electron and ic bond use the periodic table to support and explain ic bonding theory. Sep 16 2:2 PM Aug 19 11:54 AM what do you know about: bonding? Q: What force holds s together? Q: What is a chemical bond? Q: Why do some s bond together, while others do not? Q: What does all of this have to do with the periodic table? Sep 3 3:45 PM Sep 1 10:13 AM Q: What is a chemical bond? A bond is an electrostatic attract between s or s. electrostatic Atoms are attracted to one another largely because of their structure. The structure of an can be understood by examining the periodic table. So take out your new boyfriend/girlfriend: the periodic table! electro = electricity static = unmoving, at rest But where does this attract come from? Sep 16 2:30 PM Aug 19 1:22 PM 1

2 Some Back story... The form we use today was created in 1869 by Russian Scientist Dmetri Mendeleev. Of course, there were some weirdos that didn't quite fit in. He arranged the elements into three main categories: non metals metals non metals metals metaloids Although hydrogen isn't a metal, it still gets put on the metal side (for weirdness). metalloids Aug 20 11:06 AM Aug 20 11:14 AM And like any table, it has its cliques and special groups: Each group had its special properties: alkali metals react violently with water halogens form poisonous gases and travel in pairs But the noble gases were interesting: they will not form bonds with other elements. noble (inert) gases They seemed very content and stable. Aug 20 11:1 AM Aug 20 11:21 AM So let's go back to the quest: Where does the electrostatic attract come from? In order to answer why most elements form bonds through electrostatic attracts, we will look at why noble gases DON'T form bonds. To answer this quest, let's look at the structure of a noble gas like helium (He). He This is what we would call the Dalton Model of an. Tricky, non? Aug 20 11:26 AM Aug 20 11:30 AM 2

3 Recall the three parts of an : The protons and neutrons (omitted) exist inside the nucleus at the centre of the. We know He has 2 protons and electrons because its ic number is 2. n The electrons go around the nucleus in paths called orbitals. Bohr Model Another way of drawing helium out is to use an electron orbital diagram. 2 p He electron orbital diagram Notice, He (g) has two electrons in its orbital. Aug 20 11:35 AM Aug 20 11:40 AM Let's look at another noble gas: neon (Ne). 8 Ar has three orbitals. Notice a pattern starting to form... Ne has 10 protons and electrons. 10 p Ne has two electron orbitals: the first has 2 e 's, the second has 8 e 's. 18 p Ar Ne The outer orbital in an is called the valence orbital. This is where all the magic is going to happen. Let's look at another noble gas, argon (Ar): Electrons fill the orbitals in a set pattern: *Note: this only holds for the first 20 elements. Aug 20 11:44 AM Aug 20 11:51 AM The electrons in the first 20 elements follow this pattern. All noble gases complete the pattern perfectly. This makes them extremely stable. But not all of them can complete the pattern. Some fall short. Look! Na does not fit the pattern! Its valence orbital has 1 electron instead of 8. So what is the big deal about that? Why do s have to have full valence orbitals? Let's examine the structure of one such that falls short of the noble gases: an of sodium. Na Atoms want full valence orbitals in order to become stable, like a noble gas. All s really want in life is this stability. So how can Na become stable? Aug 20 11:04 AM Sep 16 2:40 PM 3

4 In order to become stable, Na needs a full valence orbital, like a noble gas. In fact, all s want to lose or gain electrons to become like the nearest noble gas. So it can either gain e 's, or lose 1 e. In order to get a full valence orbital, Na will lose one electron. lose e Which would you rather do? Na We also know from the periodic table that Na can lose one electron to gain a charge of 1. An which gains or loses an electron to become more stable is called an. Aug 20 12:06 PM Aug 19 1:32 PM So now we have a Na. Let's make another 8, just so Na won't be lonely. Cl Let's make an of chlorine, called a chloride. 1 p Cl gain e 1 p Cl It is easiest for Cl to gain one electron and fill its valence. This makes chlorine a negative (as it gained one extra negative charge). Again, this can be determined from the periodic table. Aug 20 12:11 PM Aug 19 1:52 PM so, back to the quest... Where does this electrostatic attract come from? When the sodium and chloride are bonded, the extra electron from the sodium is transferred to the chloride. There is an exchange of electrons between the s. Ans: it comes from the difference in charge between s (from gaining or losing electrons). Now, let's tackle the second quest: What makes up a chemical bond? 1 p lose e gain e Na 8 1 p This is called ic bonding. Cl Cl Aug 19 1:59 PM Sep 16 2:58 PM 4

5 So, in short... Q: Why do s form chemical bonds? A: All s wish to have a full outermost, or valence, energy level. Properties of the Table The table is arranged into groups or families (up and down) and periods or rows (left and right). By forming bonds, s fill their valence orbital. Now, let's look at some properties of the periodic table that can help solidify the idea of electron structure and bonding. Sep 16 3:01 PM Aug 20 12:28 PM The group number corresponds to the number of valence electrons in the (if you ignore the transit metals). Notice how elements in the same group have the same number of valence electrons. This accounts for their similar chemical properties. (ex: alkali earth metals explode in water) i.e. Group IA s have 1 valence e 's, group IIA have 2 valence e 's, etc. Aug 20 12:31 PM Aug 20 12:32 PM The period indicates the number of electron energy levels in the electron orbital diagram. Using this informat, it is easy to construct electron orbital diagrams to see how s become s and identify the structures needed for ic bonding. Try these examples: Aug 20 12:32 PM Aug 20 12:34 PM 5

6 Practice: Complete the energy level models. a) b) c) d) e) f) p p p Aug 24 2:43 PM Aug 24 2:49 PM HW: Read Pages 8 84 in Text. Practice: Page 84 Quests 1, 2, 5, 6, 10 Aug 20 10:46 AM 6