PeriodicityPeriodicity
GlencoeGlencoe
Chapter 6Chapter 6
DevelopmentDevelopmentof theof the
Modern Periodic TableModern Periodic Table1790s – 23 known elements1790s – 23 known elementsBy 1870s – 70 known elementsBy 1870s – 70 known elements1864 - John Newlands proposed arrangements by mass 1864 - John Newlands proposed arrangements by mass and properties by octavesand properties by octaves1864 – Lothar Meyer proposes arrangements by mass 1864 – Lothar Meyer proposes arrangements by mass and columns of properties—but doesn’t publish!and columns of properties—but doesn’t publish!1869 – Dmitri Mendeleev also proposed arrangements 1869 – Dmitri Mendeleev also proposed arrangements by mass and columns of properties—and announces!by mass and columns of properties—and announces! 1913 – Henry Moseley proposed arrangements by 1913 – Henry Moseley proposed arrangements by atomic number. (periodic law)atomic number. (periodic law)
Newlands’ “octaves”Newlands’ “octaves”H 1 F 8 Cl 15 Co/Ni 22 Br 29 Pd 36 I 42 Pt/Ir 50
Li 2 Na 9 K 16 Cu 23 Rb 30 Ag 37 Cs 44 Tl 53
Gl 3 Mg 10 Ca 17 Zn 25 Sr 31 Cd 34 Ba/V 45 Pb 54
Bo 4 Al 11 Cr 18 Y 24 Ce/La 33 U 40 Ta 46 Th 56
C 5 Si 12 Ti 19 In 26 Zr 32 Sn 39 W 47 Hg 52
N 6 P 13 Mn 20 As 27 Di/Mo 34 Sb 41 Nb 48 Bi 55
O 7 S 14 Fe 21 Se 28 Ro/Ru 35 Te 43 Au 49 Os 51
Shortly after, his ideas were presented to the Russian Physico-chemical Society. They were read by Professor Menschutkin because Mendeleev was ill. His ideas were then published in the main German chemistry periodical of the time, Zeitschrift fϋr Chemie.
The world’s first view of Mendeleev’s Periodic Table – an extract from Zeitschrift fϋr Chemie, 1869. Click here for a translation
Key “landmarks”Key “landmarks”of theof the
modern periodic tablemodern periodic tablePeriods (horizontal)Periods (horizontal)Groups/families (vertical)Groups/families (vertical)Representative elementsRepresentative elements s & p blocks & p block Groups 1A – 8AGroups 1A – 8A Groups 1,2,13,14,15,16,17,18Groups 1,2,13,14,15,16,17,18
Transition elementsTransition elements d block (f block = “inner transition elements”)d block (f block = “inner transition elements”) Groups 1B – 8BGroups 1B – 8B Groups 3 - 12Groups 3 - 12
Other notable classifications:Other notable classifications:
MetalsMetals Alkali (group 1)Alkali (group 1) Alkaline (group 2)Alkaline (group 2)
MetalloidsMetalloids
NonmetalsNonmetals Halogens (group 17)Halogens (group 17) Noble gases (group 18)Noble gases (group 18)
Organizing Elements by Electron Organizing Elements by Electron ConfigurationConfiguration
Valence ElectronsValence Electrons Atoms in the same group have similar chemical Atoms in the same group have similar chemical
properties b/c they have the same # if valence properties b/c they have the same # if valence electronselectrons
Valence Electrons and PeriodsValence Electrons and Periods Energy level of valence electrons indicates the Energy level of valence electrons indicates the
period on the PTperiod on the PT
Valence Electrons and Group NumberValence Electrons and Group Number Group # = # valence electronsGroup # = # valence electrons Exception: HeliumException: Helium
The s-, p-, d-, and f- block elementsThe s-, p-, d-, and f- block elements s-blocks-block p-blockp-block d-blockd-block f-blockf-block
Periodic trendsPeriodic trends
Vary systemicallyVary systemically across a period (horizontally)across a period (horizontally) along a group (vertically)along a group (vertically)
Atomic radiiAtomic radii
Based on probability of electron cloud, Based on probability of electron cloud, therefore, defined by how closely an atom therefore, defined by how closely an atom lies to a neighboring atomlies to a neighboring atom
DECREASES to the right across a periodDECREASES to the right across a period Due to larger nuclear attraction Due to larger nuclear attraction
INCREASES down a groupINCREASES down a group Due to more “layers” of electronsDue to more “layers” of electrons
Ionic RadiiIonic Radii
Ions (charged atoms) form when electrons Ions (charged atoms) form when electrons are gained or lost….(the number of are gained or lost….(the number of protons and electrons don’t match!)protons and electrons don’t match!)
DECREASES to the right across a period DECREASES to the right across a period (in two phases)(in two phases)
INCREASES down a groupINCREASES down a group
Ionization EnergyIonization Energy
Defined as “amount of energy required to remove an Defined as “amount of energy required to remove an electron from a gaseous atom”electron from a gaseous atom”
11stst ionization energy ionization energy 22ndnd ionization energy ionization energy Etc.Etc.
Think of this as the atom’s ability to hold onto its valence electron!Think of this as the atom’s ability to hold onto its valence electron!
INCREASES across a periodINCREASES across a period Harder to remove e-Harder to remove e- Positive energy means “harder”Positive energy means “harder”
DECREASES down a groupDECREASES down a group Easier to remove e-Easier to remove e- More negative energy means “easier” or “more stable”More negative energy means “easier” or “more stable”
Element I1 I2 I3 I4 I5 I6 I7
Na 490 4560
Mg 735 1445 7730
Al 580 1815 2740 11,600
Si 780 1575 3220 4350 16,100
P 1060 1890 2905 4950 6270 21,200
Octet RuleOctet Rule
Atoms tend to gain, lose, or share Atoms tend to gain, lose, or share electrons in order to acquire a full set of electrons in order to acquire a full set of eight valence electronseight valence electrons Note chemical stability of noble gasesNote chemical stability of noble gases Predicts ionic charge of main block elementsPredicts ionic charge of main block elements
CATIONS—positively charged ions CATIONS—positively charged ions (lost e-)(lost e-)
ANIONS—negatively charged ions ANIONS—negatively charged ions (gained e-)(gained e-)
Electron AffinityElectron Affinity
Energy associated with adding an electron to an Energy associated with adding an electron to an atom’s electron cloud---atom’s electron cloud---think of the opposite of think of the opposite of Ionization Energy…but same effect!Ionization Energy…but same effect!
INCREASES (but the energy gets more negative INCREASES (but the energy gets more negative = means “more stable”) across period= means “more stable”) across periodDECREASES (but the energy value gets more DECREASES (but the energy value gets more positive = means “more difficult”) down grouppositive = means “more difficult”) down group
Therefore, a great idea!....Therefore, a great idea!....
ElectronegativityElectronegativity
IndicationIndication of the relative ability of the atom of the relative ability of the atom to attract electrons in a chemical bondto attract electrons in a chemical bond Think of this quantity as how strongly an atom Think of this quantity as how strongly an atom
might want to gain an electron.might want to gain an electron.
Arbitrary rating scaled to 4.0…..Arbitrary rating scaled to 4.0….. Most electronegative element is fluorine with Most electronegative element is fluorine with
3.983.98
INCREASES across a periodINCREASES across a periodDECREASES down a groupDECREASES down a group
Summary of TrendsSummary of Trends
Top Related