Presentation on theme: "Chapter 6.2 – Ionic and Covalent Bonding"— Presentation transcript:
1 Chapter 6.2 – Ionic and Covalent Bonding ObjectivesWhy do atoms form bonds?How do ionic bonds form?What do atoms joined by covalent bonds share?What gives metals their distinctive properties?How are polyatomic ions similar to other ions?
2 Chapter 6.2 – Ionic and Covalent Bonding atoms bond when their valence electrons interact so that each atom has a full or stable electron configurationeach atom wants to fill its outer s and p sublevels2 basic kinds of compoundseach type of compound has a different kind of bond
3 Chapter 6.2 – Ionic and Covalent Bonding ionic compoundsformed from ionshave ionic bonds – an attractive force between oppositely charged ions, which form when electrons are transferred from one to anotherone atom loses one or more electrons and another atom or atoms gains themthe oppositely charged ions are then attracted to each other and form an ionic bond
4 Chapter 6.2 – Ionic and Covalent Bonding ionic compounds form strong networksbecause they do not form individual molecules, to write the chemical formulas use the smallest ratio of one ion to another, called the formula unitNaCl 1:1 Na2O 2:1 AlBr :3smallest ratio means they will not be divisible by each other and get a whole numberwill never have an ionic compound with a 2:2, 6:3, or 2:4 ratio
5 Chapter 6.2 – Ionic and Covalent Bonding ionic bonds are very strongtherefore ionic compounds are solid at room temperature and have high melting and boiling pointssolid ionic compounds do not conduct electricity because their electrons are held tightly by the ionswhen melted or dissolved in water, the ions can move and will conduct electricity
6 Chapter 6.2 – Ionic and Covalent Bonding ionic compounds are neutralcan tell from their formula unitsNaCl Na+ Cl :1 rationeed 1 Na+ for every Cl- to be neutralMgF2 Mg F :2 rationeed 2 F- for every Mg2+ to be neutralNa2S Na+ S :1 rationeed 2 Na+ for every S2- to be neutral
7 Chapter 6.2 – Ionic and Covalent Bonding Covalent compounds –have covalent bonds – bonds formed when atoms share one or more pairs of electrons- electrons are shared so that both atoms have full outer energy levelsalso called moleculeslow melting and boiling pointsdo no conduct electricityformed between nonmetals
8 Chapter 6.2 – Ionic and Covalent Bonding the lines in a structural formula show covalent bondseach line represents 2 electrons that are shareddots around atoms represent unshared electronspairs of electrons stay together in structural formulas
9 Chapter 6.2 – Ionic and Covalent Bonding atoms can share multiple electronswhen this happens the bonds are strongerwhen two pairs of electrons are shared it is called a double bondwhen three pairs of electrons are shared it is called a triple bondwhen only one pair of electrons are shared it is called a single bond
10 Chapter 6.2 – Ionic and Covalent Bonding atoms do not always share electrons equallywhen electrons are not shared equally the electrons spend more time near one atom than the otherthis gives the atoms small charges and the bond is called polarpolar covalent bond –bond where electrons are shared unequally and the atoms have partial positive and negative chargesex. H2O, HF, NH3, HCl
11 Chapter 6.2 – Ionic and Covalent Bonding when atoms share electrons equally the bond is nonpolar nonpolar covalent bond – bond where electrons are shared equally and the atoms are not partially charged ex. H2, Cl2, N2, CH4, CO2
12 Chapter 6.2 – Ionic and Covalent Bonding Metals form metallic bonds –bonds between metal cations and the sea of electrons around themthe nuclei form a closest packing structurethe electrons flow around them and do not belong to any one atomthere is a sea of freely moving electronsthis allows metals to flex into sheets or wires without breakingvery strong bondshigh melting and boiling pointsconducts electricity well
13 Chapter 6.2 – Ionic and Covalent Bonding polyatomic ion –a group of covalently bonded atoms that have a chargeform ionic bonds and ionic compounds with other atomsacts as a single ion in a compoundpolyatomic ions can be positive or negativepolyatomic ions can combine with other ions or other polyatomic ions
14 Chapter 6.2 – Ionic and Covalent Bonding when more than one of a specific polyatomic ion appears in a compounds name put parentheses around(NH4)2S Al2(SO4)3 Fe3(PO4)2the charge of a polyatomic ion applies to the whole ionmany polyatomic ions have oxygen in thempolyatomic ions with many oxygen atoms end with –atepolyatomic ions with few oxygen atoms end with -ite
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