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Chapter 6.2 – Ionic and Covalent Bonding Objectives -Why do atoms form bonds? -How do ionic bonds form? -What do atoms joined by covalent bonds share?

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Presentation on theme: "Chapter 6.2 – Ionic and Covalent Bonding Objectives -Why do atoms form bonds? -How do ionic bonds form? -What do atoms joined by covalent bonds share?"— Presentation transcript:

1 Chapter 6.2 – Ionic and Covalent Bonding Objectives -Why 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 configuration -each atom wants to fill its outer s and p sublevels -2 basic kinds of compounds -each type of compound has a different kind of bond

3 Chapter 6.2 – Ionic and Covalent Bonding 1.ionic compounds -formed from ions -have ionic bonds – an attractive force between oppositely charged ions, which form when electrons are transferred from one to another -one atom loses one or more electrons and another atom or atoms gains them -the 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 networks -because they do not form individual molecules, to write the chemical formulas use the smallest ratio of one ion to another, called the formula unit NaCl 1:1Na 2 O 2:1AlBr 3 1:3 -smallest ratio means they will not be divisible by each other and get a whole number -will 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 strong -therefore ionic compounds are solid at room temperature and have high melting and boiling points -solid ionic compounds do not conduct electricity because their electrons are held tightly by the ions -when melted or dissolved in water, the ions can move and will conduct electricity

6 Chapter 6.2 – Ionic and Covalent Bonding -ionic compounds are neutral -can tell from their formula units NaCl Na + Cl - 1:1 ratio need 1 Na + for every Cl - to be neutral MgF 2 Mg 2+ F - 1:2 ratio need 2 F - for every Mg 2+ to be neutral Na 2 S Na + S 2- 2:1 ratio need 2 Na + for every S 2- 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 levels -also called molecules -low melting and boiling points -do no conduct electricity -formed between nonmetals

8 Chapter 6.2 – Ionic and Covalent Bonding -the lines in a structural formula show covalent bonds -each line represents 2 electrons that are shared -dots around atoms represent unshared electrons -pairs of electrons stay together in structural formulas

9 Chapter 6.2 – Ionic and Covalent Bonding atoms can share multiple electrons -when this happens the bonds are stronger -when two pairs of electrons are shared it is called a double bond -when three pairs of electrons are shared it is called a triple bond -when 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 equally -when electrons are not shared equally the electrons spend more time near one atom than the other -this gives the atoms small charges and the bond is called polar polar covalent bond – bond where electrons are shared unequally and the atoms have partial positive and negative charges ex. H 2 O, HF, NH 3, 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. H 2, Cl 2, N 2, CH 4, CO 2

12 Chapter 6.2 – Ionic and Covalent Bonding Metals form metallic bonds – bonds between metal cations and the sea of electrons around them -the nuclei form a closest packing structure -the electrons flow around them and do not belong to any one atom -there is a sea of freely moving electrons -this allows metals to flex into sheets or wires without breaking -very strong bonds -high melting and boiling points -conducts electricity well

13 Chapter 6.2 – Ionic and Covalent Bonding polyatomic ion – a group of covalently bonded atoms that have a charge -form ionic bonds and ionic compounds with other atoms -acts as a single ion in a compound -polyatomic ions can be positive or negative -polyatomic 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 (NH 4 ) 2 SAl 2 (SO 4 ) 3 Fe 3 (PO 4 ) 2 -the charge of a polyatomic ion applies to the whole ion -many polyatomic ions have oxygen in them -polyatomic ions with many oxygen atoms end with –ate -polyatomic ions with few oxygen atoms end with -ite


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