Download E. Oxides of Group IV elements

Ch.42 notes – P.1
Ch.42 – Group IV Elements
A. Introduction
 Group IV elements include__________,__________, ________________,
_______ and _________.
 Electronic configurations:
Carbon
Silicon
Germanium
[Kr]4d105s25p2
Tin
[Xe]4f145d106s26p2
Lead
 Carbon is a ________________, silicon and germanium are _____________,
while tin and lead are typical ____________.
B. Structure and bonding
1. Carbon
 Carbon
exists
in
two
important
allotropic
forms,
___________
and___________.
 They possess _______________________________:
Diamond
Graphite
 Diamond is a __________；graphite is used for making ____________and
_______________.
Ch.42 notes – P.2
2. Silicon and germanium
 Silicon and germanium exist as a ________________________ in which the
atoms are covalently bonded to one another.
 They are used as ______________________ in transistors.
3. Tin and lead
 Tin has two__________________: white tin (more stable) and grey tin.
 White
tin
has
______________________
and
grey
tin
has
a
________________ structure which is similar to that of diamond.
 Lead exists as a typical ______________________.
 Tin is used to plate iron to prevent it from rusting; lead is used as a protective
shield from radioactivity and used in accumulators.
Ex.
1. Describe the trend of electrical conductivities of the group IV elements.
Ch.42 notes – P.3
C. Variation in physical properties
1. Melting point
 The melting points show a
general ______________ on
going down the group.
 Diamond has giant covalent
structure, it needs a great
amount of energy to break
the _________________________.
 From carbon to germanium, the bond lengths increases and the
____________________ decrease.
 Tin and lead have metallic structures and with these, there is ___________
__________ strong metallic bonds to bring about melting. Also, in both of
these metals, only two of the four valence electrons are delocalized to form
metallic bonds (_________________).
Ch.42 notes – P.4
2. Boiling point
 The general trend and explanation of the variation in boiling point are
similar to those for melting point.
 Germanium has an abnormally high boiling point. The probable explanation
is that germanium changes to _____________________________________
in the liquid state and each atom has four valence electrons participate in the
formation of metallic bonds.
Ch.42 notes – P.5
D. Chlorides of Group IV elements
 All group IV elements form ___________________ and they are
___________ at room temperature.
 They are all _____________________________with a tetrahedral shape.
 Although each M-Cl bond is polar, the molecule as a whole has
____________________________ because it has a symmetrical shape.
 Only germanium, tin and lead form _______________, GeCl2, SnCl2 and
PbCl2.
 They exist as _____________________ at room temperature and pressure.
 Germanium(II) chloride and tin(II) chloride are ______________________
while lead(II) chloride is ________________________.
 A general trend is observed when going down the group. The relative
stability of the ______oxidation state______________, and the _____
oxidation state becomes more______________.
Ch.42 notes – P.6
Ex.
1. Refer to the electronegativities of carbon, silicon and germanium,
predict which of their M-Cl bond has the highest ionic character.
2. SiCl4 is readily hydrolyzed in water while CCl4 is stable to water. Give
an explanation.
E. Oxides of Group IV elements
 There are two series of oxides: ______________ (MO) and ____________
(MO2).
 All group IV elements except silicon from the monoxides at normal
conditions. CO is a __________________ compound, GeO is a black solid,
SnO and PbO are predominantly__________ solids.
 In
going
down
the
group,
there
is
a
relative
____________________________ of the monoxides(oxidation state of +2)
relative to the dioxides (oxidation state of +4).
Ch.42 notes – P.7
Monoxide
Formula Bond type Stability
Dioxide
Formula
Bond type
Stability
Carbon
Silicon
Germanium
Tin
Lead
Ex.
1. Carbon dioxide exists as a gas while the dioxides of other group IV
elements are crystalline solids at room temperature and pressure.
Explain.
Ch.42 notes – P.8
2. Explain why Lead(IV) oxide is an oxidizing agent.
3. Given:
Bonding
Enthalpy (kJmol-1)
C-C
348
Si-Si
176
C-O
360
Si-O
374
Explain why carbon catenates to form chains and rings, which are
stable in air while no compounds containing Si-Si bonds are found in
nature.
Ch.42 notes – P.9
F. Silicon
 Silicon is the______________ most abundant element found in the Earth’s
crust.
 It is commonly found as__________________________ in a variety of forms
such as sand, quartz and flint. It is also found as____________ in rocks and
clay.
 Silicon
can
be
obtained
from
silica
by
_____________
____________________ in an electric furnace.
SiO2(s) + C(s)

 Extremely pure silicon an be obtained by the reaction silicon(IV) chloride
with hydrogen, followed by _________________________ of the resultant
silicon.
SiCl4(s) + 2 H2(g)

Silicon is the basic material for making ___________________________.
Other uses include making steel and aluminium _____________.
Ch.42 notes – P.10
G. Silicates
1. Basic unit of silicates
 Silicates are compounds of silicon, oxygen and one or more metals.
 Silicates are the largest and the most complicated class of minerals. About
30% of all minerals are silicates.
 The basic chemical unit of silicates is the ____________ anion, which has a
__________________ shape.
 A few silicate minerals contain SiO44- as discrete ions, and they are known as
_____________________, e.g. Zircon, ZiSiO4.
2. Structures of silicates
 The SiO44- tetrahedral can be joined up to form chain, sheet sheet or network
silicates by sharing oxygen atoms, e.g. Si2O76-.
Ch.42 notes – P.11
a) Chain silicates
 When two oxygen atoms of an SiO44- tetrahedron with other SiO44- tetrahedra,
the silicates form a __________ or an _____________________.
 Chain silicates tend to have ________________________________________
because the individual chains of tetrahedral can be separated much more
easily than the chains themselves that can be broken.
 In some ______________, the fibrous nature is resulted from the long-chain
silicate anions present in the mineral.
b) Sheet silicates
 When each SiO44- tetrahedron _______________________________ atoms
with neighbouring SiO44- tetrahedra, sheet silicates are formed.
Ch.42 notes – P.12
 Sheet silicate anions are found in ___________ and ___________.
 Since only weak van der Waals’ forces exist between the sheets of the SiO44anions, mica and clay readily cleave into_______________.
c) Network silicates
 The mineral quartz consists of SiO44- tetrahedral in which_____________
__________________ with adjacent SiO44- tetrahedra.
 Another group of network silicates is the ______________ group. Every
oxygen atom is shared between SiO44- tetrahedra, but some of the tetrahedra
have____________ at their centers instead of silicon. Aluminium has one
electron
less
to
share
than
silicon
atom.
This
allows
the
__________________ ______________ to atoms of sodium, potassium or
calcium.