Ionic Compound Formulas.

Transcription

1 Ionic Compound Formulas

2 Valence Electrons Electrons are divided between core and valence electrons B 1s 2 2s 2 2p 1 Core = [He], valence = 2s 2 2p 1 Br [Ar] 3d 10 4s 2 4p 5 Core = [Ar] 3d 10, valence = 4s 2 4p 5

3 Rules of the Game No. of valence electrons of a main group atom = Atoms Group like number to either (for A empty groups) or fill their outermost level. Since the outer level contains two s electrons and six p electrons (d & f are always in lower levels), the optimum number of electrons is eight. This is called the octet rule.

4 Keep an Eye On Those Ions! Electrons are lost or gained like they always are with ions negative ions have gained electrons, positive ions have lost electrons The electrons that are lost or gained should be added/removed from the highest energy level (not the highest orbital in energy!)

5 Keep an Eye On Those Ions! Tin Atom: [Kr] 5s 2 4d 10 5p 2 Sn +4 ion: [Kr] 4d 10 Sn +2 ion: [Kr] 5s 2 4d 10 Note that the electrons came out of the highest energy level, not the highest energy orbital!

6 Keep an Eye On Those Ions! Bromine Atom: [Ar] 4s 2 3d 10 4p 5 Br - ion: [Ar] 4s 2 3d 10 4p 6 Note that the electrons went into the highest energy level, not the highest energy orbital!

7 Octet Rule!Octet rule says that atoms like to have full outer shells of only eight electrons.!atoms will lose or gain valence electrons to make their outer shells full with eight electrons, and they do this by bonding with other atoms.

8 Lewis Dot Structure (Electron Dot Structure)! A Lewis dot structure is a quick and easy diagram that shows the valence electrons in an element. In a Lewis structure, the nucleus of the element is represented by its symbol. The valence electrons are represented by dots placed around the symbol in pairs.

9 Across Period 2

10 How this relates to the bond! A chemical bond is the force that holds two atoms together they can form by the attraction between the positive nucleus of one atom and the negative electrons of another atoms OR by the attraction of negative and positively charged atoms, this week and next we will discuss both interactions.

11 SUMMARY!Lewis electron dot diagrams use dots to represent valence electrons around an atomic symbol.!lewis electron dot diagrams for ions have less (for cations) or more (for anions) dots than the corresponding atom.

12 Predicting Ionic Charges Group 1: Lose 1 electron to form 1+ ions H + Li + Na + K +

13 Predicting Ionic Charges Group 2: Loses 2 electrons to form 2+ ions Be 2+ Mg 2+ Ca 2+ Sr 2+ Ba 2+

14 Predicting Ionic Charges B 3+ Al 3+ Ga 3+ Group 13: Loses 3 electrons to form 3+ ions

15 Predicting Ionic Charges Neither! Group 13 elements rarely form ions. Group 14: Lose 4 electrons or gain 4 electrons?

16 Predicting Ionic Charges N 3- P 3- As 3- Nitride Phosphide Arsenide Group 15: Gains 3 electrons to form 3- ions

17 Predicting Ionic Charges O 2- S 2- Se 2- Oxide Sulfide Selenide Group 16: Gains 2 electrons to form 2- ions

18 Predicting Ionic Charges F 1- Cl 1- Br 1- Fluoride Chloride Bromide Group 17: Gains 1 electron to form 1- ions I 1- Iodide

19 Predicting Ionic Charges Group 18: Stable Noble gases do not form ions!

20 Predicting Ionic Charges Groups 3-12: Many transition elements have more than one possible oxidation state. Iron(II) = Fe 2+ Iron(III) = Fe 3+

21 Predicting Ionic Charges Groups 3-12: Some transition elements have only one possible oxidation state. Zinc = Zn 2+ Silver = Ag +

22 Chemical Bonds

23 Formation of Ions from Metals Ionic compounds result when metals react with nonmetals Metals lose electrons to match the number of valence electrons of their nearest noble gas Positive ions form when the number of electrons are less than the number of protons Group 1 metals ion 1+ Group 2 metals ion 2+ Group 13 metals ion 3+

24 Ionic Bond Between atoms of metals and nonmetals with very different electronegativity Bond formed by transfer of electrons Produce charged ions all states. Conductors and have high melting point. Examples; NaCl, CaCl 2, K 2 O

25 1). Ionic bond electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

26 Covalent Bond Between nonmetallic elements of similar electronegativity. Formed by sharing electron pairs Stable non-ionizing particles, they are not conductors at any state Examples; O 2, CO 2, C 2 H 6, H 2 O, SiC

27 Bonds in all the polyatomic ions and diatomics are all covalent bonds

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29 Covalent Bonding! Also called molecular bonds! A bond between two nonmetals! With ionic bonding the electrons are rearranged! In covalent bonding neutral atoms share one or more pairs of electrons The shared electrons move in a molecular orbital which is a region of high probability that is occupied by an individual electron

30 NONPOLAR when electrons are shared equally COVALENT BONDS H 2 or Cl 2

31 2. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons. Oxygen Atom Oxygen Atom Oxygen Molecule (O 2 )

32 POLAR COVALENT when electrons are shared but shared BONDS H 2 O

33 - water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

34 Formation of a Covalent Bond

35 Covalent Bonds

36 You find the electronegativity difference! difference non polar covalent (shared equally)! difference polar covalent (shared unequally electrons spend more time around the more electronegative atom)! > 2.1 ionic

37 Covalent Compounds! These are compounds that contain 2 or more NONmetals. Examples: CH 4 H 2 O SiO 2 CO 2 CO

38 Covalent Polarity! Just like in real life, when it comes to sharing, each element may not share the electrons equally with the other.! How much time an electron spends with one element compared to the other depends on the elements electronegativities.

39 Electronegativity and Polarity! Electronegativity is the tendency of an element to attract an electron. This is why the electronegativity increases as the elements get closer to the halogens (they want an electron the most)!! When two elements combine, we need to take their electronegativities in mind.

40 Two Types of Compounds Smallest piece Types of elements Melting Point Ionic Formula Unit Metal and Nonmetal Molecular/ covalent Molecule Nonmetals Bond Type Ionic Covalent Solid, liquid State solid or gas High >300ºC Low <300ºC

41 Molecular compounds made of just nonmetals smallest piece is a molecule can t be held together because of opposite charges. Held together by covalent bonds and the sharing of valence electrons.

42 Molecular compounds name tells you the number of atoms. Uses prefixes to tell you the number

43 Prefixes 1 = mono- 2 = di- 3 = tri- 4 = tetra- 5 = penta- 6 = hexa- 7 = hepta- 8 = octa-

44 Prefixes 9 = nona- 10 = deca- To write the name, write two words:

45 Prefixes 9 = nona- 10 = deca- To write the name, write two words: Prefix name Prefix name -ide

46 Prefixes 9 = nona- 10 = deca- To write the name, write two words: Prefix name Prefix name -ide One exception is we don t write mono- if there is only one of the first element.

47 Prefixes 9 = nona- 10 = deca- To write the name, write two words: Prefix name Prefix name -ide One exception is we don t write mono- if there is only one of the first element. No double vowels when writing names (oa oo)

48 Name These N 2 O Dinitrogen monoxide NO Nitrogen dioxide 2 Cl 2 O Dichlorine heptoxide 7 Carbon tetrabromide CBr 4 Carbon dioxide CO 2

49 Write formulas for these diphosphorus pentoxide P 2 O 5 tetraiodine nonoxide I 4 O 9 sulfur hexafluoride SF 6 nitrogen trioxide NO 3 carbon tetrahydride CH 4 phosphorus trifluoride PF 3

50 Acids Definition: Compounds that give off hydrogen ions when dissolved in water. Must have H in them. will always be some H next to an anion. The anion determines the name.

51 Naming acids If the anion attached to hydrogen is a main group element put the prefix hydro- and change -ide to -ic acid HCl - hydrogen ion and chloride ion hydrochloric acid H 2 S hydrogen ion and sulfide ion hydrosulfuric acid

52 Naming Acids If the acid has a polyatomic ion in it change the ending from -ate to ic or from -ite to -ous HNO 3 Hydrogen and nitrate ions Nitric acid HNO 2 Hydrogen and nitrite ions Nitrous acid USE NO HYDRO-

53 Name these HF Hydroflouric acid H 3 P Hydrophosphoric acid H 2 SO 4 H 2 SO 3 HCN H 2 CrO 4 Sulfuric acid Sulfurous acid Cyanic acid Chromic acid

54 Writing Acid Formulas Hydrogen will always be first name will tell you the anion make the charges cancel out. Starts with hydro?- no oxygen, -ide no hydro?, -ate comes from -ic, -ite comes from -ous

55 Write formulas for these hydroiodic acid HI acetic acid HC 2 H 3 O 2 carbonic acid H 2 CO 3 phosphorous acid HPO 3 hydrobromic acid HBr

56 Review» ionic» metal + nonmetal» name the cation, name and anion and change the ending to -ide» charges must cancel» you can criss-cross charges to write subscripts in the formula

57 Review» covalent/molecular» two or more nonmetals» use prefixes to indicate # of atoms» prefix-name prefix-name-ide» don t use the prefix mono for the first atom

58 Review» Acids» Start with H» if its H and one element you name it: hydro-element name-ic acid» if its H and a poly you name it using the poly, if the poly ends in ate change the ending to ic or ite change the ending to ous then use the word acid» You MUST STILL PAY ATTENTION TO CHARGES H is +1