2Section IonsOBJECTIVES:Determine the number of valence electrons in an atom of a representative element.
3Section IonsOBJECTIVES:Explain how the octet rule applies to atoms of metallic and nonmetallic elements.
4Describe how cations and anions form. Section IonsOBJECTIVES:Describe how cations and anions form.
5Why do some elements react to form compounds and others do not Why do some elements react to form compounds and others do not? Is there any way to predict if atoms might react with each other? Is there any way to predict what chemical formulas might be formed?
6Ionic and Metallic Bonding Na 1+, Na +1 or Na+ = cation , missing 1 e-O2- = anion, gained 2 e-(the number is the charge on ion, not # of e- gained or lost,, i.e., +1 means 1 electron lost, not 1 gained.)
7Ion definitionsValence electrons: Outermost electrons. The s and p electrons in the outer energy level. The highest occupied energy level.Core electrons: are those in the energy levels below.Ion: An atom that has lost or gained an electron. Ions have a + or - charge.(Atoms are always neutral, # of p+ = # of e-)Cation: Positive Ion or metals, gained e-.Anion: Negative Ion or non-metals, Lost e-.
8Valence Electrons are…? The electrons responsible for the chemical properties of atoms, and are those in the outer energy level.Valence electrons - The s and p electrons in the outer energy levelthe highest occupied energy levelCore electrons – are those in the energy levels below.
9Keeping Track of Electrons Atoms in the same column (group)...Have the same outer electron configuration.Have the same valence electrons.The number of valence electrons are easily determined. It is the group number for representative.Group 2A: Be, Mg, Ca, etc.have 2 valence electronsGroup 8A, Noble gases has 8.
10Electron Dot diagrams are… DEF: Shows the 8 valence electrons as dot pairs around the chemical symbol.A way of showing & keeping trackof valence electrons.How to write them?Write the symbol - it represents the nucleus and inner (core) electronsPut one dot for each valence electron (8 maximum)They don’t pair up until they have to (Hund’s rule). Do 4 singles before pairs.X
11Electron Dot diagrams Single dots can be on any side.
12Valence e- highest electron energy level of an atom (ns np…where n is the same number) Nitrogen 1s2 2s2 2p Valence e-
13e- dot structures show only valence e- (single per side/then pair up) 2 dots Mg –[Ne]3s2 3p0
15valence e- determine the chemical properties of an element Alkali metals (1 ve-) - ns1 np0
16Remember s, p, d, f blocks S p 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1S1 1S2 2p1 2p2 2p32p4 2p5 2p6
17Write the e dot structures O = 1s2 2s2 2p4 Ne = Na =
18Write the e dot structures O = 1s2 2s2 2p4. Ne = 1s2 2s2 2p6 Write the e dot structures O = 1s2 2s2 2p4 Ne = 1s2 2s2 2p6 Na = 1s2 2s2 2p6 3s1 3p
19e dot structures – show valence e- as dots O = 1s2 2s2 2p4 e dot structures – show valence e- as dots O = 1s2 2s2 2p4 Ne = 1s2 2s2 2p6 Na = 1s2 2s2 2p6 3s1 3p
20octet rule – ions tend to have pseudo noble gas configuration (8 valence e-) full s and p orbitals
21Formation of CationsMetals lose electrons to attain a noble gas configuration.They make positive ions (cations)If we look at the electron configuration, it makes sense to lose electrons:Na 1s22s22p63s1 1 valence electronNa1+ 1s22s22p6 This is a noble gas configuration with 8 electrons in the outer level.
22Electron Dots For Cations Metals will have few valence electrons (usually 3 or less); calcium has only 2 valence electronsCa
23Electron Dots For Cations Metals will have few valence electronsMetals will lose the valence electronsCa
24Electron Dots For Cations Metals will have few valence electronsMetals will lose the valence electronsForming positive ionsCa2+This is named the “calcium ion”.NO DOTS are now shown for the cation.
25Electron Configurations: Anions Nonmetals gain electrons to attain noble gas configuration.They make negative ions (anions)S = 1s22s22p63s23p4 = 6 valence electronsS2- = 1s22s22p63s23p6 = noble gas configuration.Halide ions are ions from chlorine or other halogens that gain electrons
26Electron Dots For Anions Nonmetals will have many valence electrons (usually 5 or more)They will gain electrons to fill outer shell.3-P(This is called the “phosphide ion”, and should show dots)
27Stable Electron Configurations All atoms react to try and achieve a noble gas configuration.Noble gases have 2 s and 6 p electrons.8 valence electrons = already stable!This is the octet rule (8 in the outer level is particularly stable).Ar
28ATOM Na = 1s2 2s2 2p6 3s1 3p0 ION Na+1 = 1s2 2s2 2p6
29a. What is the charge of an e-. b. What is the e- config for N 3- ion a. What is the charge of an e-? b. What is the e- config for N 3- ion? c. How many e- does (B) have? d. how many valence e- does (B) have?
30Common IONIC CHARGES OF REPRESENTATIVE ELEMENTS Add to periodic table Common IONIC CHARGES OF REPRESENTATIVE ELEMENTSAdd to periodic table1+12+213+31415-316-217-1LiNaKRbCsBeMgCaSrBaAlNPAsOSSeFClBrI
32When writing S2-, what does the 2- indicate When writing S2-, what does the 2- indicate? Does this ion have more or less e than the original atom?
33Section 7.2 Ionic Bonds and Ionic Compounds OBJECTIVES:Explain the electrical charge of an ionic compound.
34Section 7.2 Ionic Bonds and Ionic Compounds OBJECTIVES:Describe three properties of ionic compounds.
35Ionic Compounds – compounds formed from cations and anions Usually a metal and a nonmetal (the charges always cancel) Na+, Cl- = NaCl
36Ionic BondingAnions and cations are held together by opposite charges (+ and -)Ionic compounds are called salts.Simplest ratio of elements in an ionic compound is called the formula unit.The bond is formed through the transfer of electrons (lose and gain)Electrons are transferred to achieve noble gas configuration (Octet Rule).
37Ionic CompoundsAlso called SALTSMade from: a CATION with an ANION (or literally from a metal combining with a nonmetal)
38Ionic BondingNaClThe metal (sodium) tends to lose its one electron from the outer level.The nonmetal (chlorine) needs to gain one more to fill its outer level, and will accept the one electron that sodium is going to lose.
39Ionic BondingNa+Cl -Note: Remember that NO DOTS are now shown for the cation!
40Chemical formula = number of atoms in a formula unit of an ionic compound (and not the charges on the ions) Formula unit = NaCl
41Ionic BondingLets do an example by combining calcium and phosphorus:CaPAll the electrons must be accounted for, and each atom will have a noble gas configuration (which is stable).
51= Ca3P2 Ionic Bonding Formula Unit This is a chemical formula, which shows the kinds and numbers of atoms in the smallest representative particle of the substance.For an ionic compound, the smallest representative particle is called a: Formula Unit
52Chemical formula = number of atoms in a formula unit of an ionic compound (and not the charges on the ions) Formula unit = NaCl
53Ionic compounds are usually brittle solids at room temperature, with repeating internal 3-D crystal patterns, that have high melting points
54Ionic bonds – electrostatic force that holds compound together
55What number of each ion do you need to make an ionic compound What number of each ion do you need to make an ionic compound? Na, F Na, S Al, N
56What number of each ion do you need to make an ionic compound. Na, F What number of each ion do you need to make an ionic compound? Na, F NaF Na, S Na2S Al, N AlN
57Metal bonds valence electrons of metal atoms can be modeled as a sea of electrons Metallic bonds = free-floating valence electrons attracted to the positively charged metal ions
58Alloys are mixtures composed of two or more elements, at least one of which is a metal
59Quick review questions Can have everyone stand up and answers following q’s to sit down.
60An ionic compound is usually formed between a metal and a __?