TUTORIAL 4 PART 2
MELISZA SOFFIA BT MUHAMMAD AMIRUL 2019214908
4) Transition metal can exhibit variable oxidation state in their compounds. Explain
the given statement .
= All transition metals exhibit a +2 oxidation state where electrons are first removed
from the 4s sub-shell.This is because the electrons in the d shell are closer to the
nucleus than the atoms in the s shell. As a result, the electrons in the highest s shell
tend to be lost first, rather than the electrons in the d shell.Since transition metals
have 5 d-orbitals which d-orbital has a variety of oxidation states. The d electrons are
fairly easy to remove, but there are certain states that are more stable than
others.The half-full set of 'd' orbitals is spherically symmetrical and has an extra
degree of stability.
5) Aqueous solution of transition metal ions tend to be colored while the main group
metal ions are colorless. Explain the phenomena.
= Colors can vary depending on the charge, number & groups of atom attach to the
metal ion (ligands).When ligands are present, some d orbitals become higher or
lower energy than before.When the d-level is not completely filled, it is possible to
promote electron from a lower energy d-orbital to a higher energy d orbital by
absorption of a photon of electromagnetic radiation (d-d transitions).The wavelength
of the light absorbed is affected by the size of the energy gap between the d orbitals.
6) Describe the following trend for transition element when going down the group
and across the period of the periodic table.
a) Atomic size
Across the period : Decrease at first, then remains relatively constant. additional
electrons are added to the inner 3d subshell resulting in stronger attraction to the
nucleus. 3d electrons shield the outer 4s electrons from the increasing of nuclear
charge.
Going down the group : Atomic size increases from Period 4 to 5 .The total number
of shells increase and orbitals get larger leading to greater size. Atomic size for
Period 5 to 6 almost the same size .The third row of transition metals contains many
more protons in their nuclei.The third row "contracts" because of these additional
protons. This effect is called the “lanthanide contraction”.
b) lonization energy
Across the period : Amount of energy required to remove an electron from its
ground state.Increase relatively little across the transition metals of a particular
period.Across the period, atomic size decreasing so electrons are more closely
attracted to the nucleus, thus the electron is more difficult to be removed.
Going down the group : Generally increases moving down a group.Because of two
factors:
1) Relatively small increase in size
2) Relatively large increase in nuclear charge.
As the element going down the group, there are just small increasing in size and the
nuclear charge increase. Atom with higher nuclear charge held electrons closely to
the nucleus. Therefore, ionization energy increase. Counter to the pattern in the
main groups.
c) Electronegativity
Across the period : The ability of an atom to attract the bonding electrons to itself.
Increase relatively little across the transition metals of a particular period.Crossing
the period, atomic size decrease. The smaller the atomic size,the higher the ability to
attract bonding to itself.
Going down the group : Increase within a group from Period 4 to 5, then generally
remains unchanged from Period 5 to 6.Down the group, atomic mass increases. The
heavier elements often have high electronegativity values.
7) Determine why the number of oxidation state decreases from Mn to Zn.
= due to the pairing of d electrons occurs after Mn.
8) Identify the chemical reactions which occur during the reduction of iron ore in the
blast furnace.
= Iron ores is reduced to Iron by CO.
Fe2O3 + 3CO → 2Fe +3 CO2
Fe3O4 + 4CO → 3Fe + 4CO2