Honors Chem Chapter 10 Periodic Properties
The position of an elem in the periodic table and its properties are determined by the electron configuration of the atom.
10.1 Radii of Atoms • Moving from top to bottom in the table, ea period represents a higher principal quantum number • \ as princ quant # incr, size of e- cloud incr • Size of atoms in ea group incr as you go down the table • Atomic radius – the radius of an atom w/out regard to surrounding atoms
10.1 Radii of Atoms • Going across in a period, all atoms have the same n • The (+) chg on the nucleus incr by 1 p+ for every elem in the period. • \Outer e- cloud is pulled in a little tighter • Atoms generally decr slightly in size from left to right across a period.
10.1 Radii of Atoms • Atomic radii increases top to bottom and right to left in the periodic table
10.2 Radii of Ions • When atoms unite to form molecs or comps, their structures become more stable • When ionic comps are formed, e- are given up by the metal (+ ion) and gained by the nonmetal (-) ion • Ex) Na has a 3s1 outer config • When it reacts w/ Cl, Cl takes this e- & becomes Cl- • Na bcomes Na+ (10 e-’s, 11 p+’s) • Na+ ion is smaller than Na atom
10.2 Radii of Ions • 2 reasons Na+ is smaller than Na • 1. + charged nucleus is attracting fewer e-’s • \ stronger nuclear attraction • 2. Na+ has only 2 energy levels, while Na has 3 • Na+ 1s22s22p6 - same as noble gas – Ne • Noble gas config is stable bec of full outer level • Noble gas config is stable bec of full outer level
10.2 Radii of Ions • Cl- is larger than Cl atom • Gains e-, 17 p+’s attracting 18 e-’s • \ weaker nuclear attraction • Stable bec of noble gas config like Ar
10.2 Radii of Ions • NaCl is a collection of = #’s of Na+ and Cl- ions • When melted or dissolved, ions are free to move & conduct a current • Solid NaCl crystal can not conduct electricity bec ions can’t move – tightly bound • Mobility of electric charge completes a circuit.
10.2 Radii of Ions • Chemists use ionic radii to discuss size of ions • Na+ is smaller than Na; Mg2+ even smaller than Mg • Loses 2 e-’s & unbalanced (+) charge is much larger than (-) charge on e- cloud • Cloud shrinks • S-2 & Cl- are larger than their atoms • Gain e-’s to form ions • (-) chg is larger than (+) chg – cloud grows • Si & P don’t easily lose e-’s • Usually for comps by sharing outer e-’s
10.2 Radii of Ions • Density is a periodic property • Densities vary in a regular way when plotted against the atomic # of the elems • Metals have high densities • Nonmetals have low densities.
Trends which apply to any row of the periodic table • Metallic ions – formed by loss of e-’s • Smaller than atoms from which they are formed • Nonmetallic ions – formed by gaining e-’s • Larger than their atoms • Metallic ions have stable outer level like the preceding noble gas. • Nonmetallic ions have stable outer level like the noble gas in the same period.
10.3 Predicting Oxidation Numbers • Outer level & highest energy e-’s are the ones involved in the rxn of atoms • Most atoms want to become stable (like noble gases) • Group 1 atoms have 1 e- in outer shell • If it loses 1 e-, it will have a noble gas config • \ oxidation # is +1 • H may also gain 1 e- to have a config like He • \ H can also have a -1 oxidation #
10.3 Predicting Oxidation Numbers • Group 2 atoms have 2 e-’s in outer level • \ lose 2 e-’s to gain stability • Oxidation # is +2 • Transition elems – highest energy e-’s not in outer level • E-’s are lost from outer (highest) energy level 1st regardless of order in e- config • May lose some lower level e-’s as well as outer level e-’s
10.3 Predicting Oxidation Numbers • Sc ends in 4s23d1 – may lose 2 e-’s & have a +2 oxid. # • *** d e-’s may be lost one at a time • \ may also lose 1 d e- & have a +3 charge too • Transition elems tend to have >1 oxid # • Vary from +1 to +8 • We may predict Sc to have +2 & +3 oxid #’s • Actually it only has a +3 oxid #
10.3 Predicting Oxidation Numbers • Ti ends in 4s23d2 – may show +2, +3, +4 (it does) • V has a max oxid # of +5 • Cr has a max oxid # of +6 • Mnhas a max oxid # of +7
10.3 Predicting Oxidation Numbers • Fe ends in 4s23d6 – has only +2 &+3 oxid #’s • +2 – gives up s e-’s • +3 – gives up s e-’s & only 1 d e- which makes a ½-full sublevel • Will not give up any more bec it will become less stable
10.3 Predicting Oxidation Numbers • Group 13 lose 3 e-’s & have +3 oxid # • Tl also has a +1 oxid # • Ends in 6s24f145d106p1 • Large diff in energy betw 6p &6s • \ may lose only 1 e- - the 6p
10.3 Predicting Oxidation Numbers • Group 14 may have oxid #’s of +2 or +4 • Elems in groups 15-17 have outer shells that are > half full • \ tendency to gain e-’s to achieve an octet • Group 15 gains 3 e-’s, \oxid # of -3 • Group 16 gains 2 e-’s, \oxid # of -2 • Group 17 gains 1 e-, \oxid # of -1 • It’s poss for them to lose & have (+) oxid #’s • Tendency to lose e-’s incr as you move down a column.
10.3 Predicting Oxidation Numbers • For “A” group elems – column # gives maximum (+) oxid # for elems in that column • Column # minus 8 gives lowest possoxid # • For “B” group elems, the maximum oxid # is the same as the column label
10.4 First Ionization Energy • The attraction of an atom for e-’s determines the type of bond formed on a comp. • Ionization Energy – energy required to remove an e- from an atom • First Ionization Energy – energy required to remove the most loosely held e- in an atom • (KJ/mole)
10.4 First Ionization Energy • Ionization energies are periodic properties • Tend to incr as Z incr in a period (left to right) • Tend to decr as you move down a group • Metals have low ioniz energies • Nonmetals have high ioniz energies
10.4 First Ionization Energy • As you go dn a column, outer level e-’s are farther from the nucleus • \ held less tightly • Also, there’s a decr in nuclear attraction betw outer e-’s & nucleus bec of other e-’s betw them • Shielding Effect • E-’s are held less tightly – less energy to remove them • \ lower ionization energy
10.4 First Ionization Energy • As you move across the table in a period, atoms get smaller bec of increased nuclear attraction • E-’s held tighter, \ higher ionization energy
10.4 First Ionization Energy • There are deviations from the expected as we move across the table • Small decrbetw Be (1s22s2) & B (1s22s22p1) • Be – a 2s e- must be removed from a fairly stable atom • B – a lone 2p e- must be removed • Ion is more stable, \ takes less energy • Small decrbetw N(1s22s22p3) & O (1s22s22p4) • N is more stable w/ ½-filled sublevel
Factors Affecting Ionization Energy • Nuclear Charge (nuclear attraction) • Shielding Effect • Radius • Sublevel
10.5 Multiple Ionization Energies • It’s poss to meas 2nd, 3rd, … ionization energies of an atom • Ionization energy incr w/ removal of ea successive e- • Ex) 2ndioniz energy of Al ~ 3x the first • 1stioniz removes a p e- • 2ndioniz removes an s e- from a full sublevel • 3rdioniz energy is ~ 1 ½ X the 2nd • 2nd & 3rd e-’s are in the same s sublevel
10.5 Multiple Ionization Energies • **Successive ioniz energies incrbec the nuclear chg remains the same as the # of e-’s decr • \ remaining e-’s are held even tighter • 4thioniz energy of Al is ~ 4 X the 3rd • After 3rd e- is removed, 4th e- is in lower energy level • Closer to nucleus, \ held MUCH tighter
10.6 Electron Affinities • Attraction of an atom for an e- (usually an extra e-) • Factors which affect e- affinity are the same as those affecting ioniz. Energy • Generally – as e- affinity incr, ioniz energy incr • Metals have a low e- affinity • Nonmetals have a high e- affinity
10.6 Electron Affinities • Electron affinities show periodic trends • Not as regular as ioniz energies • As you go across a period, e- affinities incr • Greater nuclear attraction for e- bec of incr nuclear charge • There are exceptions in this trend bec of full & ½-full sublevels
All these properties are involved when atoms react w/ ea other to form compounds. • Props of compounds depend on the structures of their atoms.