Transcript Introducing the Elements - Paul M. Dorman High School

Introducing the Elements
The Element Song
1869: Dmitri Mendeleev
• Russian chemist
• Arranged elements in
tabular form so that
elements with similar
properties were in the
same column
• When listed in order
by mass, elements
generally repeat
properties in groups
of 8 (Law of Octaves)
The First Periodic Table
• Most tables at the time listed elements by mass
• Mendeleev also arranged elements by mass, but
left several “holes” in his table and occasionally
reversed the order of elements to fit the
properties of others in that column
• The “holes” were later filled in with newly
discovered elements that had the properties
predicted by Mendeleev’s table.
• The reason for the reversal of elements was
explained later by Henry Moseley, who noted
that the elements were in order by atomic
number (number of protons) rather than by mass
Know the following Elements
1-20, 24-30, 33, 35-38, 47, 48, 50, 53-56,
78, 79, 80, 82, 86, 92
 Names and symbols

1. Sodium
2. Mercury
3. Zinc
4. Bromine
5. Calcium
6. Fluorine
7. Helium
8. Manganese
9. Nickel
10.Uranium
11. C
12. O
13. Pb
14. Sn
15. Cr
16. Mg
17. Ba
18. K
19. Si
20. Ag
1. boron
2. berylluim
3. iron
4. chlorine
5. lithium
6. magnesium
7. argon
8. cobalt
9. potassium
10.phosphorous
11. Al
12. Cd
13. As
14. Pt
15. Cu
16. Sr
17. Ba
18. Ne
19. Rn
20. Kr
Hydrogen
• Most abundant element in
the universe
Why?
• Makes up most the mass
of stars
• Can be H+ (hydrogen
ion) or H- (hydride ion)
• Used in Fuel Cells: How
Stuff Works
• In Fusion, H is converted
to He
Alkali Metals: Li, Na, K, Rb, Cs, Fr
• Most reactive of the (Not found in nature in elemental form)
metals, +1 ions
• Stored under kerosene or
mineral oil
• Na and K most important
• Na2CO3 and NaHCO3 two
important compounds
• K is an important plant
nutrient (macronutrient)
• Fertilizers: N-P-K
Alkaline Earth Metals: Be, Mg, Ca, Sr, Ba, Ra
• Harder, more dense,
and less reactive than
alkali metals
• Ca, Sr, and Ba most
alike
• Hard Water: Ca2+
and Mg2+ ions
• Epsom salt: MgSO4
Boiler Scale
…..more on the alkaline earths
• CaCO3 is limestone
becomes marble
• Limestone is most
abundant rock in the
earth’s crust
• CaO “Lime” or
“quicklime”
• CaSO4 “Plaster of
Paris” (building
material)
Plaster of Paris footprints
Do You Know?
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•
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Most abundant element in the universe?
Most abundant rock in the earth’s crust?
Formula for the “plaster of Paris”?
Ions found in “hard” water?
Three numbers of fertilizer?
How do alkaline earth metals compare to
the alkali metals in (a) reactivity and (b)
density?
Aluminum Group: B, Al, Ga, In, Tl
• Aluminum by far the most important
• Third most abundant element in the
earth’s crust
• Important metal: abundant, light weight,
strong
• Al2O3 coating prevents corrosion
Carbon Group: C, Si, Ge, Sn, Pb
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Very diverse group of elements
C is the basis for organic compounds
CO2 and CO3-2 inorganic carbon
CO2 one of the earliest gases in the
atmosphere
• Carbon cycling one of the most important
• Two basic parts: (1) photosynthesis (2)
respiration
Disrupting the carbon cycle
•
CO2 is a greenhouse
gas (GWP=1)
Increasing
concentration by:
•
1.
2.
Burning fossil fuels
Removing vegetation
•
Preindustrial 1800:
280 ppm
1959: 316 ppm
2010: 388 ppm
2011: 391 ppm
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Silicon - Si
• Second most
abundant element in
the Earth’s crust
• Found in clay, sand,
sandstone, silica rock,
quartz, other minerals
• Many different
bonding combinations
• Is a semiconductor
(Silicon Valley)
Tin (Sn) and Lead (Pb)
• Many Industrial Uses
• Pb is a “heavy metal” and is toxic to many
organs in the human body
• Impedes the development of the nervous
system
• Taken out of gasoline in the late 1970’s
and removed from most paints
The Halogens F, Cl, Br, I, At
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•
•
Group 17 – halogen means (salt former)
The most reactive nonmetals
F and Cl are gasses
Br is a liquid
I is a solid
Total Molar Composition of Seawater (Salinity = 35)[7]
Compone
nt
Concentration
(mol/kg)
H2O
53.6
Cl−
0.546
Na+
0.469
Mg2+
0.0528
SO2−
0.0282
4
Ca2+
0.0103
K+
0.0102
CT
0.00206
Br−
0.000844
BT
0.000416
Sr2+
0.000091
F−
0.000068
Bonding: Influences
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Valence Electrons
Nuclear Charge
Atomic Size/Radius
Distance between attractions
Screening or Shielding Effect
Valence Electrons
Core Configurations
• Why? – Shows/focuses on the valence
electrons.
• Write the configuration for arsenic.
• 1s22s22p63s23p64s23d104p3
• or
• [Ar] 4s23d104p3
• How many valence electrons?
• Write the electron configuration and orbital
notation for chlorine.
• 1s22s22p63s23p5
• Now write its core configuration.
• [Ne] 3s23p5
• How many valence electrons?
Atomic Radius: How is it measured?
• Half the distance between nuclei of two
covalently bonded atoms of the same
element.
• Why not just measure from the nucleus to
the outer edge of the atom?
Atomic Radius
Radius trends
• Group trend?
Radius increases down a group
• Why?
Adding new energy levels
• Period trend?
Radius decreases across a period
• Why?
Increasing nuclear charge has the
effect of pulling electron cloud closer.
Ions and their formation
• Cations
• Formed by the loss of
electrons
• Positively charged
• Usually formed from
metals
• Are always smaller
than the atom they
are formed from
• Anions
• Formed by the gain of
electrons
• Negatively charged
• Usually formed from
nonmetallic elements
• Are always larger
than the atom they
are formed from
Ionization Energy
• The energy required to remove an electron from
an isolated, neutral, gaseous atom.
• First ionization energy – energy required to
remove a first electron from an atom.
• Second ionization energy – energy required to
remove a second electron from an atom.
• Third ionization energy - ????
• Etc . . . .
First Ionization Energies
First Ionization energies
• Group trend – IE1 decreases down a
group. Why?
• Valence electrons are further from the
nucleus and the shielding effect is greater
down a group.
• Shielding effect – occurs when core
electrons “shield” or interfere with the
attraction that the nucleus has for the
valence electrons.
. . . IE cont. . . .
• Period trend – IE1 is larger as you move
across a period, left to right. Why?
• Atoms are smaller so valence electrons
are closer to the nucleus and . . . . .
• . . . the nuclear charge is greater with no
change in shielding effect (electrons are
going in the same energy level)
Ionization Energy Increasing Trend
Periodic Table
Successive Ionization Energies
Where do the largest jumps occur for each
Element and why do you think this happens?
Electronegativity
• A measure of the ability of an atom to
attract electrons to itself when bonded to
other atoms.
Electronegativity
Electronegativities
1. Place these elements in order of increasing:
Ge, P, N, and Si
(a) atomic radius
(b) first ionization energy
(c) electronegativity
2. Write the core configuration for the following
elements: S, Ca, Sn
3. How many valence electrons does each
element in #2 have?