The Structure of Matter: Ionic & Covalent Bonding Ionic bond - the attractive force that holds oppositely charged ions together; anions are - ones, but cations are + ones. Ionic bond - the attractive force that holds oppositely charged ions together; anions are - ones, but cations are + ones. Formula unit – smallest unit of an ionic compound like one Na+ & one Cl- together for table salt Formula unit – smallest unit of an ionic compound like one Na+ & one Cl- together for table salt

Ionic & Covalent Bonding 2 Because ionic compounds have network structure, discussing just one “molecule” of salt makes little sense. Because ionic compounds have network structure, discussing just one “molecule” of salt makes little sense. Metallic bond – formed by attraction between + charged metal ions & nearby electrons Metallic bond – formed by attraction between + charged metal ions & nearby electrons

Ionic & Covalent Bonding 3 Covalent bond – formed when atoms share 1 or more pairs of electrons Covalent bond – formed when atoms share 1 or more pairs of electrons Nonpolar covalent bond – atoms share equally Nonpolar covalent bond – atoms share equally

Ionic & Covalent Bonding 4 Polar covalent bonds – atoms share electrons unequally Polar covalent bonds – atoms share electrons unequally Polyatomic ion – 2 or more covalently bonded atoms that act like 1 ion, charged atom; Polyatomic ion – 2 or more covalently bonded atoms that act like 1 ion, charged atom; Memorize Table 4-3 on p Memorize Table 4-3 on p. 122.

Chapter 4.2 “To Do/Answer” List Why do atoms sometimes join to form bonds? Why do atoms sometimes join to form bonds? Why do some atoms transfer valence electrons to form ionic bonds while others share these electrons to form covalent bonds? Why do some atoms transfer valence electrons to form ionic bonds while others share these electrons to form covalent bonds?

Chapter 4.2 “To Do/Answer” List 2 What’s the difference between ionic, covalent & metallic bonds? What’s the difference between ionic, covalent & metallic bonds? Compare the properties of substances with different types of bonds. Compare the properties of substances with different types of bonds.

What Holds Bonded Atoms Together? Recall that all atoms “want” a full outermost energy level Recall that all atoms “want” a full outermost energy level In bonded atoms, this level is full of electrons. In bonded atoms, this level is full of electrons.

What Holds Bonded Atoms Together? 2 Bonding happens when valence electrons interact with the positively charged nucleii of nearby atoms. Bonding happens when valence electrons interact with the positively charged nucleii of nearby atoms. Recall that protons are + and in the nucleus but that electrons are – and like a cloud around the same atomic nucleus so they hide the +. Recall that protons are + and in the nucleus but that electrons are – and like a cloud around the same atomic nucleus so they hide the +.

What Holds Bonded Atoms Together? 3 This way atoms show no net charge until home electrons leave or guest ones arrive. This way atoms show no net charge until home electrons leave or guest ones arrive. Bonds can bend and stretch like springs without breaking. Bonds can bend and stretch like springs without breaking.

What Holds Bonded Atoms Together? 4 Most bond lengths are averages because nucleii don’t stay the same distance apart. Most bond lengths are averages because nucleii don’t stay the same distance apart.

Ionic Bonds Formed between oppositely charged ions. Formed between oppositely charged ions. Cations – plus charged ions that come from atoms of metal elements like ones in Group 1, the alkali metals. Cations – plus charged ions that come from atoms of metal elements like ones in Group 1, the alkali metals.

Ionic Bonds 2 Anions – minus charged atoms that come from nonmetal elements like a halogen or oxygen. Anions – minus charged atoms that come from nonmetal elements like a halogen or oxygen. Electron transfer forms ionic bonds which have networks of ions not clusters of molecules. Electron transfer forms ionic bonds which have networks of ions not clusters of molecules.

Ionic Bonds 3 Ionic compounds conduct electricity or moving charges when dissolved in water. Ionic compounds conduct electricity or moving charges when dissolved in water. Ions are charged and free to flow if dissolved but locked in network if not. Ions are charged and free to flow if dissolved but locked in network if not.

Ionic Bonds 4 Writing considerations is optional. Writing considerations is optional. Now consider a grandmotherly, cookie baking kind of lady who just so happens to have corns, bunions and heaps of humped hammertoes. Now consider a grandmotherly, cookie baking kind of lady who just so happens to have corns, bunions and heaps of humped hammertoes.

Ionic Bonds 5 She needs your advice on when it’s safe to blow dry the hair on her legs while soaking her feet in a foot tub. She needs your advice on when it’s safe to blow dry the hair on her legs while soaking her feet in a foot tub. She usually adds Epsom salt to hot water in the tub and rubs mineral oil on her hands before treating her feet. She usually adds Epsom salt to hot water in the tub and rubs mineral oil on her hands before treating her feet.

Ionic Bonds 6 Be careful because the wrong information could cause seizures, suffocation & biting off of the tongue. Be careful because the wrong information could cause seizures, suffocation & biting off of the tongue.

Ionic Bonds 7 Liquefaction of the brain, ruptured eyes and torturous death are some other signs of high voltage electrocution. Liquefaction of the brain, ruptured eyes and torturous death are some other signs of high voltage electrocution. What advise would guarantee her safety while soaking and blow drying? What advise would guarantee her safety while soaking and blow drying?

Metallic Bonds Electrons move freely between metal ions. Electrons move freely between metal ions. This quality allows them to be malleable (bendable and stretchable) and to conduct electricity as solids. This quality allows them to be malleable (bendable and stretchable) and to conduct electricity as solids.

Metallic Bonds 2 Close packing of atoms in metals causes overlap of their outermost energy levels. Close packing of atoms in metals causes overlap of their outermost energy levels. This gives electrons added mobility to flow (electricity) or slide (malleability) by each other. This gives electrons added mobility to flow (electricity) or slide (malleability) by each other.

Covalent Bonds These bonds are found in molecular compounds of joined non charged nonmetal atoms. These bonds are found in molecular compounds of joined non charged nonmetal atoms. Except for those with network structures, covalent compounds have low melting and boiling points. Except for those with network structures, covalent compounds have low melting and boiling points.

Covalent Bonds 2 Atoms joined by covalent bonds share electrons equally (nonpolar) or unequally (polar). Atoms joined by covalent bonds share electrons equally (nonpolar) or unequally (polar). Each atom starts with 7 valence electrons solo. Each atom starts with 7 valence electrons solo. Bonded, each atom shares 1 electron so that both have 8. Bonded, each atom shares 1 electron so that both have 8.

Covalent Bonds 3 Equality of sharing depends on how much each “partner wants” the shared electron. Equality of sharing depends on how much each “partner wants” the shared electron. More “need” gets more of the share. Consider H 2 O. The electrons stay closer to O. More “need” gets more of the share. Consider H 2 O. The electrons stay closer to O.

Polyatomic Ions Compounds with both covalent and ionic bonds include polyatomic ions. Compounds with both covalent and ionic bonds include polyatomic ions. Oppositely charged polyatomic ions like other ions can bond to form ionic compounds. Oppositely charged polyatomic ions like other ions can bond to form ionic compounds.

Polyatomic Ions 2 (NH 4 ) 2 SO 4 where NH 4 + & SO 4 2- join shows how important parentheses are to keep clear what the polyatomic ions, PI. (NH 4 ) 2 SO 4 where NH 4 + & SO 4 2- join shows how important parentheses are to keep clear what the polyatomic ions, PI. The parentheses also help show how to combine the PI to make compounds with no net charge. The parentheses also help show how to combine the PI to make compounds with no net charge.

Polyatomic Ions 2 Above, two NH 4 + plus one SO 4 2- = 2 plus charges with 1 negative 2 charge for a total charge of zero, ( ). Above, two NH 4 + plus one SO 4 2- = 2 plus charges with 1 negative 2 charge for a total charge of zero, ( ). Some polyatomic anion names relate to their oxygen content, for example, –ate ends names for anions with one more O atom and –ite for the anions with 1 less. Some polyatomic anion names relate to their oxygen content, for example, –ate ends names for anions with one more O atom and –ite for the anions with 1 less. NO 3 - is nitrate, but NO 2 - is nitrite. NO 3 - is nitrate, but NO 2 - is nitrite.