General Chemistry I
Properties of the Elements
Development of the Periodic Table
elements exist in compounds
Century saw huge increase in the number of elements discovered
31 in 1800 to 63 in 1865
based on properties and in increasing atomic weight
considered ‘Father of the Periodic Table’
more adamant about it’s use
‘holes’ for missing elements
his table to predict the properties
elements were discovered, predicted properties were very close to observed.
with atomic weight arrangement
< Ar and I < Te
stated when techniques became more accurate, these problems would resolve
found that emitted X-rays were of different frequencies for different elements.
frequency increased as the atomic mass increases
were Ar, K and Te, I
to assign an ‘Atomic number’
to number of protons
to identify holes
Electron Shells and Atomic Size
does not have ‘sharp’ boundaries
define a ‘probability surface’ (typically 90%) that is a hard surface
proposed by Lewis
to an onion
in QM atom
n Examine noble gas electronic structure
n He – 1s2
n Ne – 1s2 2s2 2p6
n Ar – 1s2 2s2 2p6 3s2
n What is the ‘radial electron density’ for these
idea of shells
overlap of the shells
as ‘clean’ as an onion
is first shell closer to the nucleus for Ar than Ne
n Non-bonding radius
n Closest atoms will approach before electron-electron
n Bonding atomic radius
n Distance between two like nuclei in a chemical bond.
atomic properties depend on atomic size.
a group, size increases as we go down a group.
a period, size decreases as we go across (left to right) a period.
why size increases top to bottom
charge increases L-R
held tighter (closer)
Problems: 1 – 15 odd
required to remove an electron from an atom/cation
electron removed, 1st ionization energy
electron, 2nd ionization energy
jump occurs when you start removing core electrons.
First Ionization Energies
n 1st ionization energies decrease from top
to bottom in a family.
n 1st ionization energies generally
increase from L-R across a period.
change that occurs when an electron is added to an atom in the gaseous state.
more negative the electron affinity, the greater the attraction for an electron
value means energy is released.
may be released or absorbed when an electron is added.
n Not as ‘clean’ as ionization energies
n Generally become less negative from top to bottom
n Left to right generally more negative
n MANY exceptions
Problems: 17 – 29 odd
Metals vs. Nonmetals
n Malleable (sheets)
n Ductile (wires)
n Solids, except Hg
n MP from –39OC to 1900OC (Cr)
n Low ionization energies
n Form cations
n Transition metal cations often have variable charge
n Many have +2 charge
n Loss of ns electrons
n Metal/nonmetal generally form ionic compounds
n Soluble metal oxides basic
n Na2O+H2O ->2NaOH
character of oxides also demonstrated by reaction with acids
greatly in appearance
n Non lustrous
n Poor conductors
n MP generally lower
n Diamond @ 3570OC
n May be s, l, or g
n Solids range from very soft to very hard
n Tend to form anions
n Form molecules with other nonmetals
n Nonmetal oxides are acidic
n CO2+H2O -> H2CO3
n CO2, SO2, SO3, NOx
main contributors to acid rain
metallic/some nonmetallic characteristics.
Problems: 31 – 39 odd
Group Trends – Active Metals
isolated from ashes
in nature as compounds or ions
/ K+ important for intracellular transport
dominated by loss of single electron
-> M+ + e-
metals formed by electrolysis
from molten NaCl (801OC)
hydrides with H
electron to hydrogen to form H-
directly with nonmetals to form ionic compounds
with water to produce H2(g)
Reaction with Oxygen
– forms Li2O
in water to form lithium hydroxide
alkali metals form peroxides
peroxide bond is quite unstable!
not colored unless combined with a colored anion.
emit characteristic colors in a flame.
Alkaline Earth Metals
to alkali metals
dominated by the loss of 2 electrons
as reactive as alkali metals
are more stable when refined
protected by coating of MgO
be used as building material
IIA metals must be protected from air/water.
and Ca essential for living organisms.
Group Trends - Nonmetals
be considered it’s own family!
because both loss of 1 electron and gain of 1 electron gives a stable configuration.
typical of nonmetals
dominated by H+ ion
Group VI A
is a gas – all others solids
nonmetal to metal
oxygen – 2 forms
(O2) and ozone (O3)
‘oxidize’ most other elements
oxides (O2-), peroxides (O22-) and superoxides
decompose to form O2
common form S8
to gain electrons to form sulfides
more complex than oxygen
from solid (F2, Cl2) to liquid (Br2) to solid
dominated by the formation of anions by gaining electrons.
remove electrons from anything
for uranium enrichment and glass etching
product of electrolysis of molten salt
slowly with water
HCl and HOCl
as disinfectant for water
soluble halides with most metals
of two liquid elements at room temp.
similar to chlorine
shells s and p orbitals filled
few compounds of noble gases known
that are known are for the heavier noble gases (lower I1) with
Problems: 41 – 55 odd