3Valence e- what do we know… Which group on the periodic table, do you notice, always has all it’s valence electron shell full? The Noble Gases. This is very significant… Why??Because every element wants to have a full outer shell of valence e- – because then it is completely stable and never has to react. Every element wants to be a noble gas
4So what happens when atoms meet? When 2 atoms move close together, their valence electrons interact, and they form a chemical bond between them if they are a good pair (more stable together than apart)Having a full valence shell is what each element wants! So it will bind with other elements that make that happen!
5Ionic Compounds2 or more elements bonded together where at least 1 is a metal and 1 is a non-metalEg. NaCl, LiF
6Covalent Compounds2 or more elements bonded together where all are non-metals.Eg. CCl4, NiF2
7IonsThey are Atoms that have a + or – charge (due to losing or gaining electrons) -they are no longer neutral.
8When atoms have the same # of protons and electrons – the atom is neutral. And it is called an ATOM. When an atom loses or gains electrons from another element – it gets a charge and is now called an ION.Ions form when a METAL and a NON-METAL combine to form a new compound. They create an IONIC BOND between them.In an ionic bond, e- are transferred (not shared)
10Why might Beryllium want to only have 2 e- instead of the original 4? BERYLLIUM ION2+Why might Beryllium want to only have 2 e- instead of the original 4?2 positive protons left over… so …
11Let’s recap… + Has a charge (Not Neutral) ATOMNo charge(Neutral)Same # of protons as electronsIONHas a charge (Not Neutral)Protons stay the same, but a different # of electrons+Or -
12So how did the Ion get a charge? Every atom in the periodic table wants to be just like the nearest NOBLE GAS, because it has full outer shell of e- and is stable – that is what every atom wants.Notice that the metals have more electrons than the stable noble gas, and that non-metals don’t have enough electrons to be a noble gas.
13Metals tend to give up e- to become more stable (metals are givers - positive elements) Non-metals tend to gain or take e- to become more stable. (non-metals are takers – negative elements)
14What do you notice about these 2 elements?? P: 11N:12P: 17N:19Sodium AtomChlorine AtomIf Sodium loses 1e-, it would look like Neon (a noble gas with 10e-)If Chlorine gains 1e-, it would look like Argon (a noble gas with 18e-)
15Atom 11 e- Atom 17 e- ION 10 e- ION 18 e- So why does Na get a + charge??Because it gave up an electron ( got rid of a “-” charge) – so it now has 1 more proton than e-, so 1+ charge!* Remember – Givers are happy (POSITIVE)*Sharing is caring!!Chlorine is a taker – takers are selfish and are very negative.Chlorine has received an extra e-, so it’s got more e- than p+, so it’s 1-.We form NaClAtom 11 e-Atom 17 e-ION10 e-ION18 e-
16What do they look like now that they have become IONS?? P: 11N:12P: 17N:19Chlorine ION 1-Sodium ION 1+
17Two types of IonsMetals that give up e- to form “+” charged IONS are called CATIONSEg. Mg2+, Li1+, Al3+, etc…Non-metals that take e- to form “-” charge IONS are called ANIONSEg. S2- , F1- , N3-, etc…
18Let’s recap… Takers of e- Givers of e- They are gaining e- Become negativeThe # of e- they gain, is the number of - charges they get.Eg. Take 3 e- = 3- chargeCalled AnionsGivers of e-They are losing e-Become positiveThe # of e- they lose, is the number of + charges they get.Eg. Give up 3 e- = 3+ chargeCalled Cations
19Take a look… +1 P: 11 P: 11 N:12 N:12 Bohr model of SODIUM “ION” 1 valence e- gone (now 10 e-)Na 1+Bohr model of a SODIUM “ATOM”All e- there (11).Na
20Now you try it… +2 P: 12 P: 12 N:12 N:12 Bohr model of a Magnesium “ATOM”All e- there (12).Bohr model of Magnesium “ION”2 valence e- gone (now 10e-) like NeonMg 2+
21Try again… -2 P: 8 P: 8 N:8 N:8 Bohr model of a Oxygen “ATOM” All e- there (8).Bohr model of Oxygen “ION”2 valence e- added (now 10 e-) –like Neon!O 2-
22Let’s Recap…All elements want to have a full outer shell of valence e-, just like their nearest noble gas.If an element gives up e-, it becomes an ION with a + charge (CATION)If an element takes an e-, it becomes an ION with a – charge (ANION)Notice that the ion charges of each element are given on your periodic table in the top right hand corner – called the COMBINING CAPACITY.The combining capacity helps you predict the # of e- the element will gain or lose.
23But wait a minute…Notice on your periodic table, that many of the transition metals have more that 1 charge/combining capacity.That means that they can form ions in more than 1 way. Elements with more than 1 charge are called MULTI-VALENT.Eg. Iron (Fe) is multivalent because it has a charge of 2+ or 3+, so it can either lose 2 e- or 3 e- to become Fe 2+ or Fe 3+It just depends on what it bonds with.2+3+
25Can you answer these questions… Can you draw the Bohr model of H2?Why would 2 Hydrogens be happy to bond together?1p+0n1p+0n
26Try some for Lewis … N F Ar Mg Remember, up to 4 e-, you put separately on each side of the symbol, once you get to 5, you have to start pairing up.1) Magnesium Ion 2) Nitrogen Ion3) Fluorine Ion 4) Argon Ion?2+3-MgN1-FAr
27Lewis Diagrams of ionsLewis diagrams make drawing ions, and ionic bonds much less work than Bohr diagrams.–2+–• •• •• •• ••• •• •• •• •• •• •• ••• •• •• •• ••• •BeClClBeClClBeClEach beryllium has two electrons to transfer away, and each chlorine wants one more electronSince Be2+ wants to donate 2 electrons and each Cl– wants to accept only one, two Cl– ions are necessaryBeryllium chloride
28+ Ionic Compounds O O 1. Mg Mg 2+ 2- Unpaired electron Or bonding pair
29Lewis Diagrams of covalent bonds Lewis diagrams of covalent bonds are also very easy.Like Bohr diagrams, valence electrons are drawn to show sharing of electrons.All atoms wish to have a full valence shell (1st orbit=2 e-, 2nd=8e-)The shared pairs of electrons are usually drawn as a straight lineSHARING IS CARING!!
31Lewis Diagrams of diatomic molecules Diatomic molecules: 2 of the same element are bondedEg. Cl2, F2, O2, etc..Try 2 Oxygens together (remember they both want 8, so how are they going to share?)• •• •• •• •• •• •• •• •• •• •• •• •OOOOOOSeveral non-metals join to form diatomic moleculesValence electrons are shared, here in two pairs!This is drawn as a double bond
32+ Diatomic Compounds F F F F Remember when it’s a diatomic compound – you draw the 1 lines between them! (Symbolizing the 4 electrons sharing!!)