Transcript Unit 4 Periodicity

Chemistry
Unit 4: The Periodic Table
and Periodicity
Outlin
e
The Elements
Element names come from a variety of sources.
elements known to the ancients… S, Sn, C, Cu
place names… Fr, Po, Ge, Eu, Am, Cf, Sc
famous people…
Es, Md, No, Rf, Bh
foreign languages… W, Fe, Au, Ag, Pb, Cu
mythology-related names… Th, Ti
names related to element properties… Hg
Background on the Periodic Table
Dmitri Mendeleev: given credit
for Periodic Table (~1870)
-- organized Table by
increasing atomic mass
-- left spaces and predicted
properties of undiscovered
elements
Mendeleev
Henry Moseley: put elements in
order of increasing
atomic number
____________.
Moseley
Describing the Periodic Table
periodic law: the properties of elements repeat
every so often
period: horizontal row; there are 7
group (family): vertical column; there are 18
18
1
1
13 14 15 16 17
2
2
3
4
5
6
7
3 4 5 6 7 8 9 10 11 12
Regions of the Table
metals: left side of Table; form cations
properties:
lustrous
(shiny)
ductile
(can pull
into wire)
good conductors
(heat and electricity)
malleable
(can hammer
into shape)
Regions of the Table (cont.)
nonmetals: right side of Table; form anions
properties: good insulators
gases or brittle solids
neon
sulfur
iodine
bromine
Ne
S8
I2
Br2
Regions of the Table (cont.)
metalloids (semimetals): “stair” between metals
and nonmetals (B, Si, Ge, As, Sb, Te, Po)
metals
computer chips
properties: in-between those of metals
and nonmetals; “semiconductors”
Si and Ge
computer chips
alkali metals: group 1 (except H); 1+ charge;
very reactive
alkaline earth metals: group 2; 2+ charge;
less reactive than alkalis
halogens: group 17; 1– charge; very reactive
noble gases: group 18; no charge; unreactive
lanthanides: elements 58–71
actinides: elements 90–103
contain f
orbitals
coinage metals: group 11 (part of the transition metals)
transition elements: groups 3–12; variable charges; d block
main block (representative) groups 1, 2, 13–18;
elements:
s and p block
alkali metals
alkaline earth metals
halogens
noble gases
lanthanides
coinage metals
(part of the transition metals)
actinides
transition elements
metalloids
main block elements
more nonmetals
hydrogen
more metals
Honors
• Trans-uranic Elements
• Elements with an atomic number greater than 92.
www.chemicool.com
• Complete data table as a group of two, defend
your decision using the form. You may write your
defense in essay form if needed. Be specific and
answer all guiding questions.
• Due next Wednesday, Jan. 15, 2014
Einsteinium (Es)
Albert Einstein
– Relativity
– E = mc2
– Offered Presidency of Israel
– Element 99
– Photoelectric effect
• Solar calculator
Curium (Cm)
• Madame Curie
– Pioneer in radioactivity
• (Ra = radium)
– 25 pounds of pitchblende ore
yields 1/1000 of a gram of
radium
– Emits 2 millions times as much
radiation as uranium
• (Rn = radon gas)
– Discovered 5 elements
– Nobel Prize (5 in Curie family)
– Born in Poland
• (Po = polonium)
Marie Curie (1876–1934)
Radium (Ra)
Radium was used as a fluorescent paint on watch dials. It was
applied with thin brushes that workers would lick to keep a fine tip.
Many people died from the exposure to radium.
Radon Gas
Zone 1 counties have a predicted average indoor radon screening
level greater than 4 pCi/L (pico curies per liter) (red zones)
Zone 2 counties have a predicted average indoor radon screening
level between 2 and 4 pCi/L (orange zones)
Zone 3 counties have a predicted average indoor radon screening
level less than 2 pCi/L (yellow zones)
Radon gas occurs naturally
from the radioactive decay
of radium. Radium is found
in small amounts in rock.
Ra  Rn + radiation
Predicted fraction of homes over 4 picocuries/liter radon
http://www.epa.gov/radon/zonemap.html
Nobelium (No)
Element 102
Inventor:
dynamite (TNT)
blasting gelatin
Nobel Prize
NO2
O2N
NO2
CH3
Trinitrotoluene
Alfred Nobel
“Merchant of Death”
Seaborgium (Sg)
Glenn Seaborg
– Separated f-block from rest of periodic table
– Worked on Manhattan Project
(Atomic bomb)
– Classified until after WW II
– Element 106
• Only living person to have an element named for
them
Silicon vs. Silicone
• Silicon (Si) element
• Silicone (…Si – O – Si…) polymer
– Sealant (caulk) prevents leaks
– Breast augmentation
No cause-and-effect relationship exists between
breast enlargement and breast cancer. Only one
researcher found a causal link.
12
Mg
24.305
Magnesium
Atomic Mass 24 amu
melting point = 650oC
silver gray metal
(1202oF)
used in flash bulbs, bombs,and flares
8th most abundant element (2.2% of Earth’s crust)
lack of Mg produces same biological effect
as alcoholism (delirium tremens)
Mendeleev’s Work!
• http://www.screencast.com/t/kg5WRCqrqc
Uh
Periodicity
The quality of being periodic;
tendency to recur at regular intervals.
Electro negativity
Tendency of an atom to attract
electrons towards itself.
Same number of valence e– = similar properties
Li 1s2 2s1
Na 1s2 2s2 2p6 3s1
In any group, the element BELOW has one more
occupied energy level than does the element ABOVE.
Li
Na
The period that an element is in is the same as the
energy level that its valence electrons are in.
in 2nd period
in 3rd period
Li
Na
v.e– in 2nd E.L.
v.e– in 3rd E.L.
Periodicity
there are trends in properties of elements
-- left-right AND up-down trends
atomic radius: the size of a neutral atom
…increases as we go
WHY? add a new energy
level each time
…decreases as we go
WHY? it has to do with…
coulombic attraction: attraction between (+) and (–)
Coulombic attraction depends on…
amount of charge
2+
2–
1+
1–
distance between charges
2+
2+
–
+
H
He
++
+ +
– –
– –
2–
2–
As we go
,
more coulombic
attraction, no new
energy level, more
pull, smaller size
shielding effect: kernel e– “shield” valence e–
from attractive force of the nucleus
v.e–
v.e–
Li
K
tougher to
remove
easier
to remove
-- caused by kernel and valence e–
repelling each other
As we go
, shielding effect increases.
ionic radius: the size of an ion
cations
Ca atom
anions
Ca2+ ion
Cl atom
Cl1– ion
20 p+
20 p+
17 p+
17 p+
20 e–
18 e–
17 e–
18 e–
Cl
Cl1–
Ca
Ca2+
cations are smaller
anions are larger
ionization energy: the energy required to remove
an e– from an atom
M + 1st I.E.
removes 1st e–
M1+ + e–
M + 2nd I.E.
M2+ + e–
M + 3rd I.E.
M3+ + e–
Each successive ionization requires
more energy than the previous one.
As we go , 1st I.E…. decreases.
(due to the shielding effect)
As we go
, 1st I.E…. increases.
electronegativity: the tendency for
a bonded atom to
attract e– to itself
Linus Pauling quantified
the electronegativity scale.
As we go , electronegativity… decreases.
As we go
, electronegativity… increases.
Summary of
Periodic Trends