Chemical Bonding BIOB111 CHEMISTRY & BIOCHEMISTRY. Session 2

Transcription

1 Chemical Bonding BIOB111 CHEMISTRY & BIOCHEMISTRY Session 2

2 Key concepts: session 2 From this session you are expected to develop an understanding of the following concepts: Concept 1: The role of subatomic particles in chemical bonding Concept 2: Location of the subatomic particles involved in chemical bonding Concept 3: Charge of subatomic particles Concept 4: Ion formation (from an atom) Concept 5: Role of valence (outer shell) electrons in covalent bonding Concept 6: Role of electronegativity in chemical bonding Concept 7: Ionic compounds Concept 8: Formation of ions from atoms Concept 9: Covalent vs ionic bonding These concepts are covered in the Conceptual multiple choice questions of tutorial 2

3 Session Overview Part 1: Role of electrons in chemical bonding Chemical bonding Valence electrons Bonding vs non-bonding electrons Octet rule Covalent bonding Part 2: Covalent bonding Electronegativity Non-polar covalent bonding Polar covalent bonding Single, double and triple covalent bonds Part 3: Ionic bonding Ion formation from atoms Ionic bonding Polyatomic ions Covalent vs ionic bonding

4 Part 1: Role of electrons in chemical bonding Chemical bonding Valence electrons Bonding vs non-bonding electrons Octet rule Covalent bonding

5 What is the difference between a diamond and charcoal? (both composed largely of carbon atoms) The chemical bonding patterns that exist between the carbon atoms

6 Chemical bonding Atoms want to connect to other atoms via chemical bonds to become more stable Stable atoms have full valence (outer) electron shells Electrons, around the outside of the nucleus, are the subatomic particles that allow an atom to form chemical bonds with other atoms Chemical bonds allow atoms to form groups called molecules Molecules that contain more than one type of atom are compounds

7 Chemical bonding A CHEMICAL BOND IS A CONNECTION BETWEEN TWO ATOMS The basis of the connection between atoms is either: TWO ATOMS SHARING ELECTRONS Is called ONE ATOM DONATING ELECTRON(S) TO ANOTHER ATOM Through this process Is called COVALENT BONDING BOTH ATOMS BECOME IONS IONIC BONDING

8 Valence electrons Electron Proton The subatomic particle responsible for chemical bonding are the atom s electrons Nucleus Neutron Specifically, the atom s unpaired valence electrons An atom s valence electron shell is the shell furthest away from the nucleus The valence electron shell is also known as the outer electron shell In the diagram, shell 2 is the valence shell In this case, shell 2 contains both paired electrons and unpaired electrons Paired electrons Shell 1 Shell 2 Unpaired electron

9 Valence electrons VALENCE ELECTRONS Can be Can be PAIRED ELECTRONS UNPAIRED ELECTRONS Are STABLE Are UNREACTIVE DO NOT CONTRIBUTE TO CHEMICAL BONDING Are UNSTABLE Are REACTIVE CONTRIBUTE TO CHEMICAL BONDING OF THE ATOM

10 Bonding vs non-bonding electrons Electron arrangement in Nitrogen s valence (outer) shell Paired valence electrons = non-bonding electrons H N H NH 3 is the covalent compound ammonia H N H N Unpaired valence electrons = bonding electron Electron H Covalent bond = 2 electrons shared between the 2 participating atoms H Simplified representation

11 Bonding vs non-bonding electrons Each elements atoms have a specific number of valence electrons Number of valence electrons: Carbon has 4 Oxygen has 6 Nucleus Electron Proton Neutron The group number of a representative element (group A) is equal to the number of valence electrons in the atom Carbon is in group IV, so it contains 4 valence electrons Paired electrons Shell 1 Shell 2 Unpaired electron Oxygen is in group VI, so it contains 6 valence electrons

12 Bonding Vs. non-bonding electrons Lewis Symbols The number of valence electrons in a representative element is the same as the elements Group No. Electron-Dot Symbols for the first 20 elements on the periodic table (below) Chemical symbol of the element surrounded by dots, with each dot representing the number of valence electrons in the atom The maximum number of valence electrons for any element is 8 electron octet Stoker 2014, Figure 4-1 p87

13 What group is nitrogen in on the periodic table? How many valence electrons does a nitrogen atom contain? Draw the Lewis symbol for a nitrogen atom.

14 The octet rule The Octet Rule: Atoms LOSE, GAIN or SHARE their valence electrons (through chemical bonding) to obtain 8 valence electrons in their outer shell An atom that has satisfied the octet rule (has 8 electrons in the valence shell) is stable The Octet rule applies to group A (Representative) elements, but not transition elements Noble gas: neon Noble gases naturally have 8 valence electrons Noble gases are very stable and unreactive, as they have satisfied the octet rule Noble gases do not react with other atoms to form chemical bonds... Ne Non-noble gas: nitrogen Ṇ. Ṇ. After covalent bonding Non-noble gas atoms form chemical bonds with each other to fill their valence electron shells (obtain 8 electrons) Allows the non-noble gas atoms to mimic the electron arrangement of a noble gas to become very stable

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16 Chemical bonding A CHEMICAL BOND IS A CONNECTION BETWEEN TWO ATOMS The basis of the connection between atoms is either: TWO ATOMS SHARING ELECTRONS Is called ONE ATOM DONATING ELECTRON(S) TO ANOTHER ATOM Through this process Is called COVALENT BONDING BOTH ATOMS BECOME IONS IONIC BONDING

17 Covalent bonding Covalent bond: Two non-metal atoms SHARE their unpaired valence electrons to fill their valence shells & become stable The two atoms that share electrons (via the covalent bond) are connected to each other A covalent bond is actually the sharing of an electron pair, with each participating atom contributing 1 electron Naming covalent compounds 1 st non-metal is named by its elemental name 2 nd non-metal is named by its elemental name + -IDE Examples: CO: Carbon monoxide CO 2 : Carbon dioxide

18 Covalent bonding Well known covalent compound: Carbon dioxide (CO 2 ) As the breakdown products of food are metabolized to produce cellular energy (ATP), CO 2 is released The blood carries the CO 2 from the cells to the lungs where the CO 2 can be exhaled Plants use CO 2, H 2 O and sunlight to produce O 2 and glucose (carbohydrate) Photosynthesis

19 Covalent bonding Covalent bond OXYGEN HAS 8 VALENCE ELECTRONS EACH HYDROGEN HAS 2 VALENCE ELECTRONS SHARED PAIRS OF ELECTRONS COUNT TOWRDS THE ELECTRON TOTAL FOR BOTH ATOMS COVALENT BOND Simplified representation Example Definition H 2 O Covalent bond ALLOWS TWO ATOMS TO CONNECT VIA SHARING A PAIR OF ELECTRONS ALL ATOMS IN THE COMPOUND HAVE FULL VALENCE ELECTRON SHELLS AND ARE STABLE

20 ATOMS FORM AS MANY COVALENT BONDS AS REQUIRED TO OBTAIN 8 VALENCE ELECTRONS RULE NUMBER OF UNPARIED VALENCE ELECTRONS = NUMBER OF COVALENT BONDS NEEDED TO FORM THE ELECTRON OCTET (8 VALENCE ELECTRONS) OXYGEN IS IN GROUP VI, SO IT CONTAINS 6 VALENCE ELECTRONS... H 2 O HYDROGEN IS IN Ȯ.. GROUP I,. SO IT CONTAINS H 2 unpaired 1 VALENCE valence electrons ELECTRON 1 unpaired valence electron OXYGEN HAS 8 VALENCE ELECTRONS, AFTER FORMING 2 COVALENT BONDS EACH HYDROGEN HAS 2 VALENCE ELECTRONS, AFTER FORMING 1 COVALENT BOND

21 Attempt Socrative questions: 1 to 4 Google Socrative and go to the student login Room name: City name followed by 1 or 2 (e.g. PERTH1) 1 for 1 st session of the week and 2 for 2 nd session of the week

22 Summary Part 1: Role of electrons in chemical bonding Chemical bonding An atoms electrons, around the outside of the nucleus, allow the atom to form chemical bonds with other atoms A chemical bond is a connection between two atoms Valence electrons Valence electrons are the electrons in the shell furthest away from the nucleus Also known as outer shell electrons Unpaired valence electrons can be shared, lost or gained to form chemical bonds with other atoms

23 Summary Part 1: Role of electrons in chemical bonding Bonding vs non-bonding electrons Bonding electrons are unpaired valence electrons that can participate in chemical bonding Reactive Non-bonding electrons are paired valence electrons that do not participate in chemical bonding Unreactive Octet rule Atoms share, lose or gain electrons to achieve a full outer shell of electrons (8 electrons) An atom or ion that satisfies the octet rule has 8 valence electrons Electron octet

24 Summary Part 1: Role of electrons in chemical bonding Covalent bonding A covalent bond occurs when two non-metal atoms share a pair of electrons One atom contributes one electron and the other atom contributes the second electron to the shared electron pair Only unpaired valence electrons (bonding electrons) can participate in covalent bonding The number of unpaired valence electrons in an atom is equal to the number of covalent bonds the atom can form Once all of the unpaired valence electrons are used for covalent bonding, the atom has a full valence electron shell (8 electrons) Satisfies the octet rule

25 Part 2: Covalent bonding Electronegativity Non-polar covalent bonding Polar covalent bonding Single, double and triple covalent bonds

26 Electronegativity Electronegativity: The capacity of an atom to attract shared electrons (from a covalent bond) to itself Electronegativity increases From left to right going across a period Going upwards within a group Non-metals have a higher electronegativities than metals Fluorine is the most electronegative atom Timberlake 2013, Figure 5, p187

27 Electronegativity ELECTRONEGATIVITY NON-METAL ATOMS WITH A HIGH ELECTRONEGATIVITY: O, N, F, Cl Definition AN ATOMS CAPACITY TO ATTRACT A SHARED PAIR OF ELECTRONS (THE ELECTRONS ARE PART OF A COVALENT BOND) NON-METAL ATOMS WITH A LOW ELECTRONEGATIVITY: H, C H Example H C H H TWO HIGH ELECTRONEGATIVITY ATOMS CONNECTED VIA A COVALENT BOND MEANS ELECTRONS ARE SHARED EQUALLY = NON-POLAR COVALENT BOND Example Cl F TWO LOW ELECTRONEGATIVITY ATOMS CONNECTED VIA A COVALENT BOND MEANS ELECTRONS ARE SHARED EQUALLY = NON-POLAR COVALENT BOND

28 Electronegativity ELECTRONEGATIVITY NON-METAL ATOMS WITH A HIGH ELECTRONEGATIVITY: O, N, F, Cl Definition AN ATOMS CAPACITY TO ATTRACT A SHARED PAIR OF ELECTRONS (THE ELECTRONS ARE PART OF A COVALENT BOND) NON-METAL ATOMS WITH A LOW ELECTRONEGATIVITY: H, C O H H COVALENT BOND BETWEEN ONE HIGH ELECTRONEGATIVITY ATOM AND ONE LOW ELECTRONEGATIVITY ATOM MEANS ELECTRONS ARE NOT SHARED EQUALLY = POLAR COVALENT BOND Example Example H N H H

29 Polar Vs. non-polar covalent bonding Non-polar covalent bond The atoms that participate in the covalent bond share electrons equally Due to both atoms having similar electronegativities The shared electrons are equally attracted to both atoms involved in the covalent bond Example: the shared electrons are equally attracted to Cl and F O Cl F H H Polar covalent bond The atoms that participate in the covalent bond share electrons unequally Due to atoms having different electronegativities The shared electrons are more attracted to the high electronegativity atom than the low electronegativity atom involved in the covalent bond Example: the shared electrons are more attracted to O than H

30 Polar covalent bond Polar covalent bonds present in H 2 O Polar covalent bond Simplified representation O δ- δ + H O H H H Partial negative charge δ + Polar Covalent bond Partial positive charge Shared electrons are more attracted to oxygen than hydrogen, as oxygen has a higher electronegativity than hydrogen With the shared pair of negative electrons being more attracted to oxygen, oxygen has a partial negative charge (δ - ) Partial charges are not as strong as the true positive and negative charges present in ions With the shared pair of negative electrons being less attracted to hydrogen, hydrogen has a partial positive charge (δ + )

31 Non-polar covalent bond Non-polar covalent bonds present in CH 4 H H C H Simplified representation H H C Non-polar Covalent bond H Non-polar Covalent bond H H The shared pair of electrons are equally attracted to carbon and hydrogen, as carbon and hydrogen have similar electronegativities The shared pair of electrons are equally close to both the carbon and hydrogen atoms

32 Single, double and triple covalent bonds Non-metal atoms share their unpaired valence electrons with each other to form covalent bonds Allows the atoms to connect together to form covalent compounds Once all of the atoms unpaired valence electrons are paired, the atom is stable The atoms have satisfied the octet rule Stoker 2014, p Depending on the atom type (dictates the number of unpaired valence electrons), atoms form single, double or triple covalent bonds (with other atoms) to fill their valence electron shells SINGLE COVALENT BOND Sharing 1 pair of electrons shared between two atoms DOUBLE COVALENT BOND Sharing 2 pairs of electrons shared between two atoms TRIPLE COVALENT BOND Sharing 3 pairs of electrons shared between two atoms ClF CO 2 N 2 Cl F C O O N N

33 Single, double and triple covalent bonds Carbon Contains 4 unpaired valence electrons Each unpaired valence electron can form 1 covalent bond Carbon forms 4 covalent bonds to obtain 8 valence electrons C Nitrogen Contains 3 unpaired valence electrons Nitrogen forms 3 covalent bonds to obtain 8 valence electrons N

34 Single, double and triple covalent bonds Oxygen Contains 2 unpaired valence electrons Oxygen forms 2 covalent bonds to obtain 8 valence electrons O Hydrogen and halogen atoms Contain 1 unpaired valence electron Hydrogen forms 1 covalent bonds to obtain 2 valence electrons Halogen atoms such as chlorine and fluorine form 1 covalent bond to obtain 8 valence electrons H F H F

35 Key concept: Electron sharing between non-metal atoms What type of chemical bond allows hydrogen and oxygen atoms to form H 2 O? Which type of atom are the electrons most attracted to within H 2 O? Why? Why are the hydrogen atoms within the H 2 O molecules δ + and the oxygen atom is δ -? Are the oxygen and hydrogen atoms within H 2 O actually charged?

36 Attempt Socrative questions: 5 and 6 Google Socrative and go to the student login Room name: City name followed by 1 or 2 (e.g. PERTH1) 1 for 1 st session of the week and 2 for 2 nd session of the week

37 Part 2: Covalent bonding Electronegativity Electronegativity is an atoms capacity to attract a shared pair of electrons (from a covalent bond) to itself O, N, Cl and F are high electronegativity atoms H, C are low electronegativity atoms Non-polar covalent bonding The two non-metal atoms involved in the non-polar covalent bond have similar electronegativities, meaning the electrons are equally attracted to both atoms E.g. CH 4 or ClF

38 Part 2: Covalent bonding Polar covalent bonding The two non-metal atoms involved in the polar covalent bond have different electronegativities, meaning the electrons are more attracted to the atom with the higher electronegativity E.g. H 2 O The shared electrons (from a covalent bond) are more attracted to the oxygen atom than the hydrogen atoms Single, double and triple covalent bonds Depending on the number of unpaired valence electrons, some atom types can form either single, double or triple covalent bonds to fill their valence electron shell E.g. Hydrogen only needs to form 1 covalent bond to fill its electron shells, so hydrogen can only form a single covalent bond

39 Part 3: Ionic bonding Ion formation from atoms Ionic bonding Polyatomic ions Covalent vs ionic bonding

40 Chemical bonding A CHEMICAL BOND IS A CONNECTION BETWEEN TWO ATOMS The basis of the connection between atoms is either: TWO ATOMS SHARING ELECTRONS Is called ONE ATOM DONATING ELECTRON(S) TO ANOTHER ATOM Through this process Is called COVALENT BONDING BOTH ATOMS BECOME IONS IONIC BONDING

41 The octet rule The Octet Rule: Atoms LOSE, GAIN or SHARE their valence electrons (through chemical bonding) to obtain 8 valence electrons in their outer shell An atom that has satisfied the octet rule (has 8 electrons in the valence shell) is stable The Octet rule applies to group A (Representative) elements, but not transition elements Noble gas: neon... Ne.. After Noble gases naturally have 8 valence electrons Noble gases are very stable and unreactive, as they have satisfied the octet rule Noble gases do not react with other atoms to form chemical bonds Non-noble gas: sodium ionic bonding Non-noble gas atoms form chemical bonds with each other to fill their valence electron shells (obtain 8 electrons) Allows the non-noble gas atoms to mimic the electron arrangement of a noble gas to become very stable

42 Ion formation from atoms An Atom has no charge and is overall neutral When forming ionic bonds, an atom loses or gains 1 or more electrons, which converts the atom into an Ion Once an atom has lost or gained an electron it is a charged ion Ions can have either a POSITIVE or NEGATIVE charge Depending on whether the atom lost or gained electrons + ion (cation) Loss of electrons Neutral atom Gain of electrons - ion (anion)

43 Ion formation from atoms Cation A cation is a positively charged ion Forms when an atom LOSES electron(s) from its valence shell The atom becomes less negative by losing a negative electron, which causes the atom to become a positively charged ion E.g. Na atom loses one electron to form the Na + ion Metal atoms lose electrons and become positively charged ions Sodium atom loses 1 valence electron to form the positive sodium ion Na (8 valence electrons in shell 2) Sodium atom (1 valence electron in shell 3) + Na Positive sodium ion (8 valence electrons in shell 2)

44 Ion formation from atoms Anion A anion is a negatively charged ion Forms when an atom GAINS electrons into its valence shell The atom becomes more negative by gaining a negative electron, which causes the atom to form a negatively charged ion E.g. O atom gains two electrons to form the O 2- ion Non-metal atoms gain electrons to becomes negatively charged ions O Oxygen atom gains 2 valence electrons to form the negative oxygen ion O (8 valence electrons) 2- Oxygen atom (6 valence electrons) Negative oxygen ion (8 valence electrons)

45 Na Sodium atom (1 valence electron in shell 3) Sodium atom loses 1 valence electron (donating the electron to the oxygen atom) to form the positive sodium ion (8 valence electrons in shell 2) + Na Positive sodium ion (8 valence electrons in shell 2) O Oxygen atom (6 valence electrons) Na Sodium atom (1 valence electron in shell 3) Oxygen atom gains 2 valence electrons (from 2 different sodium atoms) to form the negative oxygen ion (8 valence electrons) O Sodium atom loses 1 valence electron (donating the electron to the oxygen atom) to form the positive sodium ion (8 valence electrons in shell 2) Negative oxygen ion (8 valence electrons) Na 2- + Positive sodium ion (8 valence electrons in shell 2) O 2- Na + Na + Ionic compound: Sodium oxide (Na 2 O) Contains ionic bonds between the sodium and oxygen ions

46 Ion formation from atoms The number of valence electrons in a representative element is the same as the elements Group No. E.g. group I elements have 1 valence electron Group VI elements have 6 valence electrons Representative elements forming ions The maximum number of valence electrons for any element is 8 electron octet Atoms with 3 or less valence electrons lose electrons to obtain 8 valence electrons Atoms turn into positive ions (cations) by losing electrons Atoms with 4 or more valence electrons gain electrons to obtain 8 valence electrons Atoms turn into negative ions (anions) by gaining electrons Adapted from Stoker 2014, Figure 4-8 p104

47 Ion formation from atoms Transition elements can form more than 1 type of positive ion (cation) because Octet rule does not apply A Roman number is placed into brackets after the name of the metal indicating the charge of the ion Ion Correct Name Common Name Fe 2+ Iron (II) ion Ferrous Fe 3+ Iron (III) ion Ferric Cu + Copper (I) ion Cuprous Cu 2+ Copper (II) ion Cupric Transition elements forming ions 3 exceptions that form only 1 cation: Ag + = Silver ion Zn 2+ = Zinc ion Cd 2+ = Cadmium ion

48 Ionic bonding Ionic bond: One metal atom gives away electron(s) (loses electrons) which are accepted by one non-metal atom (gains electrons) Both atoms involved in the ionic bond become ions Metal is a positive ion (cation) Non-metal is a negative ion (anion) Both ions have full valence shells and are stable Ionic compound sodium chloride Na + Cl -

49 Ionic bonding Ionic bonds are present in ionic compounds Ionic compounds contain many metal cations and non-metal anions Ratio of anions and cations allows the overall charge to be balanced (neutral) Within an ionic compound, the positive charge of the metal cation is attracted to the negative charge of the non-metal anion Ionic compounds form solids and are crystalline when arranged in a lattice Naming ionic compounds Name the metal cation & the non-metal anion Subscripts are never mentioned Examples:» MgS: Magnesium Sulfide» CaCl 2 : Calcium Chloride Stoker 2014, Figure 4-4b p99

50 Ionic bonding Important ionic compound: NaCl (aka table salt) Salt was so expensive in the middle ages that is was commonly referred to as white gold Salt opens up the taste receptors in your tongue Enhancing sweet and sour flavours, while suppressing bitterness Too much or too little salt in the body is fatal Required to maintain normal fluid levels in the body s compartments Also assists in maintaining an adequate blood pressure

51 Ionic bonding Na Sodium atom turned into positive sodium ion by losing 1 electron Na + Sodium donates an electron to chlorine Na + Cl - Forms the ionic compound sodium chloride Cl Chlorine atom turned into negative chloride ion by gaining 1 electron Cl -

52 Ionic bonding Total charge of an ionic compound must be neutral The number of positive charges must equal the number of negative charges Ca loses 2 electrons to become positively charged (cation), Ca 2+ Cl gains 1 electron to become a negatively charged (anion), Cl - Does not exist in nature Ca + Cl 1 Ca 1 Cl Ca 2+ + Cl charges 1 charge CaCl 1 Ca 1 Cl INCORRECT: Charges Unbalanced

53 Ionic bonding Total charge of an ionic compound must be neutral The number of positive charges must equal the number of negative charges Ca loses 2 electrons to become positively charged (cation), Ca 2+ Cl gains 1 electron to become a negatively charged (anion), Cl - Ca + 2Cl Ca Cl - CaCl 2 1 Ca 2 Cl 2 + charges 2 charges 1 Ca 2 Cl Overall net Charge of the ionic compound is zero CORRECT: Charges balanced

54 Polyatomic ions Polyatomic ions: A polyatomic ion is a group of non-metal atoms that form a covalent compound and carry a charge Polyatomic ions normally have a negative charge Polyatomic ions play important roles in metabolism E.g. there are three phosphate ions in ATP (cellular energy source) Formula Name or ion Formula Name of Ion NH 4 + Ammonium CO 3 2- Carbonate OH - Hydroxide HCO 3 - Hydrogen carbonate or Bicarbonate NO 2 - Nitrite PO 4 3- Phosphate NO 3 - Nitrate HPO 4 2- Hydrogen phosphate SO 3 2- Sulfite H 2 PO 4 - Dihydrogen phosphate SO 4 2- Sulfate Adapted from Stoker 2014, Table 4-3 p107

55 Covalent Vs. ionic bonding Covalent bonding Only occurs between two non-metal atoms Never involves metal atoms Two atoms involved in the covalent bond share electrons End result: Participating atoms that form covalent bonds are part of a covalent compound Atoms obtain full valence electron shells E.g. H 2 O H O H Ionic bonding Only occurs between one metal atom and one non-metal atom Never involves two metal atoms Never involves two non-metal atoms The metal atom loses an electron, while the non-metal atom accepts the electron End result: The participating atoms which are converted into ions form the ionic compound The ions obtain full valence electron shells E.g. NaCl

56 Key concept: bonding between charged ions Do two ions with opposite charges attract or repel each other? What would happen if two ions with the same charge were close to each other? What type of bond forms between a positive metal cation and a negative non-metal anion? Does the sodium (Na) atom lose or gain an electron when it reacts with chlorine (Cl) atom? How does the loss and gain of electrons help the atoms form a chemical bond?

57 Attempt Socrative questions: 7 to 10 Google Socrative and go to the student login Room name: City name followed by 1 or 2 (e.g. PERTH1) 1 for 1 st session of the week and 2 for 2 nd session of the week

58 Part 3: Ionic bonding Ion formation from atoms Atoms that lose electrons form positive ions (cations) The atom loses negative charge becoming a positively charged ion E.g. Na loses and electron to become Na + Atoms that gain electrons form negative ions (anions) The atom gains negative charge becoming a negatively charged ion E.g. Cl gains an electron to become Cl - Ionic bonding A metal atom donates electron(s) to a non-metal atom (acceptor) causing both atoms to form ions The positive charge of the cation (formed from metal atom) is attracted to the negative charge of the anion (formed from non-metal atom) and are held close together in an ionic compound Ionic compounds must have an equal number of positive and negative charges

59 Part 3: Ionic bonding Polyatomic ions A polyatomic ion is a group of non-metal atoms that form a compound and carry a charge Polyatomic ions normally carry a negative charge Covalent vs ionic bonding Covalent bonding always occurs between two non-metal atoms 2 electrons are shared between the two participating non-metal atoms in a covalent bond Ionic bonding always occurs between one metal atom and one non-metal atom The atoms form ions when the metal atom loses an electron and the non-metal atom gains an electron

60 Readings & Resources Stoker, HS 2014, General, Organic and Biological Chemistry, 7 th edn, Brooks/Cole, Cengage Learning, Belmont, CA. Stoker, HS 2004, General, Organic and Biological Chemistry, 3 rd edn, Houghton Mifflin, Boston, MA. Timberlake, KC 2013, General, organic, and biological chemistry: structures of life, 4 th edn, Pearson, Boston, MA. Alberts, B, Johnson, A, Lewis, J, Raff, M, Roberts, K & Walter P 2008, Molecular biology of the cell, 5 th edn, Garland Science, New York. Berg, JM, Tymoczko, JL & Stryer, L 2012, Biochemistry, 7 th edn, W.H. Freeman, New York. Dominiczak, MH 2007, Flesh and bones of metabolism, Elsevier Mosby, Edinburgh. Tortora, GJ & Derrickson, B 2014, Principles of Anatomy and Physiology, 14 th edn, John Wiley & Sons, Hoboken, NJ. Tortora, GJ & Grabowski, SR 2003, Principles of Anatomy and Physiology, 10 th edn, John Wiley & Sons, New York, NY.

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