Transcript Chapter 6 Per table and trends PP

Chapter 6
Periodic Law and Periodic Table
Historical background
 Before 1800, 23 elements known
 By 1870, 70 elements identified
 No pattern to tie them together known
 1864, J. Newlands noticed when elements
arranged by mass
 1st and 8th element similar
 2nd and 9th element similar, so on.
 He called pattern an octave. Did not work for all.
Mendeleev
 Noticed patterns while writing a book on
elements.
 Noticed that as mass increased, there is
a repeating of characteristics of
elements.
 Also realized that some elements were
not discovered yet.
 Predicted properties of those, and was
found to be correct when discovered.
 Were some trouble spots on P.Table
(Te,I)
 Accdg. to Mendeleev, Periodic law stated
that the characteristics of the elements
were a periodic (repeating) function of
their atomic masses.
Moseley
 Discovered the proton.
 Called the #protons the atomic number.
 Realized this could “fix” Mendeleev’s P.T.
problems.
 This changed P. Law to be based on
atomic number, not mass.(Te, I switched)
 “Chemical and Physical properties repeat
(are periodic) when arranged by at. no.”
Modern Periodic Table
 Has columns and rows of elements.
 Columns are GROUPS or FAMILIES
 Very similar in chem and phys. activity
 Not identical, though.
 Rows are called PERIODS
 Elements in a period are not at all alike.
Classification of elements
Metals
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Left and middle of P. Table
Majority of elements
Shiny (lustrous)
Good conductors of heat and electricity
Malleable
Ductile
GR. IA alkali metals-most reactive
GRIIB alkaline earthmetals, less reactive
Group B Elements
transition elements
 Transition metals
 Families 3-12 on PT
 Inner Transition
Metals
 Lanthanide Series 4f
block
 Actinide Series 5f
block
Nonmetals
 Upper right of PT.
 P block
 Group 7A halogens
 very reactive
 Need to gain 1 e-
 Group 8A noble gases
 Very unreactive
 Filled levels
Metalloids
 Border of stair step line on PT.
 Have phys. & chemical characteristics of
both metals and nonmetals
Write E config of Main
Groups
 These groups or families of elements
have similar phys. and chem.
characteristics.
 Reason is found in their e- config. They
are so similar to each other.
 Same number of valence (outer) e- cause
similar reactivity.
S block
 Group IA, IIA
 Group IA [ ]s1 config.
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Only 1 outer eThat e- easily lost
Very reactive (most of all metals)
Alkali metals
 Group 2A alkaline earth metals
 2 outer e Fairly easily lost, fairly reactive
 Config. ends in s2 (those lost)
P block Elements
 3A through 8A families (IIIA-VIIIA)
 Have filled or partially filled orbitals
 Have various reactivity depending on
number of outer e
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8A (noble gases)
Very stable
Very UNreactive
Don’t need any more e- , levels filled
D Block Elements
 Transition metals
 Largest block
 Have filled outer s orbital and filled or
partially filled d orbitals.
F block Elements
 Contain inner transition metals
 Have filled outer s sublevel and filled or
partially filled f orbitals
 Number of orbitals and e- held:
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Sblock 1 orb/level, up to 2e in each
P block, 3 orb/level, up to 6e total in each levl
D block, 5 orb/level, up to 10 e total in each
F block, 7orb/level, up to 14 e total in each
Periodic Trends
Graphing Calc Activity
 Many properties or characteristics of
elements change in predictable patterns.
 Atomic Radius
 Direct measure of atom’s size.
 Atoms get smaller L→R on P.Table
 Because more pro+ are added to nucleus to
pull more tightly on e cloud.
 Atoms get largerbecause more levels of e
are added to outside. (Onion and layers)
Ionic Radius
 Atoms gain or lose e to have only filled
levels
 These + or – particles that result are
IONS.
 Ions will have the same no. pro+ as atom
of that element. (Only e change)
 The more e added to an atom, the larger
the ion will be.
 The more e lost, the smaller the ion.
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S_2 larger than S atom. (18 e/16e)
Cl- larger than Cl. (18e/17e)
Na+ smaller than Na atom. (10e/11e)
Mg+2 smaller than Mg atom (10e/12e)
Ionization Energy
 Amount of energy needed to pull off the
outer e from an atom. (produces a + ion)
 Atoms on Left of P.Table hold their e
loosely and easily lose them.
 Atoms on Right (P Block) of P.T. hold e
tightly because they would rather gain
than lose e.
 I.E. increases L→R
 I.E. decreases because as atoms get
larger the outer e are further from the
nucleus and attraction from pro+.
Octet Rule
 We have hinted at this idea Atoms tend to gain, lose, or share e to
obtain a full set of 8 outer e (s and p
blocks)
 H and He are filled with 2 e, no p block at
all.
Electronegativity
 Ability of an atom to attract e to itself
within a chemical bond.
 Arbitrary units assigned to elements up to
3.98 (F is most e negative )
 Cs and Fr (opp corner from F) are least.
 Whichever element in bond has largest
value pulls e more toward itself. (E
greedy)
 EN inc→, EN dec.