RESULTS:
Before
After
Figure 1 (a): Reaction of Nickel (II) chloride Figure 1 (b): pH of Nickel (II) chloride
Before
After
Figure 2 (a): Reaction of Iron (III) chloride Figure 2 (b): pH of Iron (III) chloride
After
Before
Figure 3(a): Reaction of Copper (II) sulfate Figure 3(b): pH of Copper (II) sulfate
DISCUSSION:
The properties of transition metals are largely dependent on the electronic configuration of the electrons in the outer shell and in the penultimate outer shell. The transition elements readily form alloys with themselves and with other elements. The atomic size is constant since the electrons in the outer most shells have similar environments. The low ionization potentials mean that the elements show variable valency states by loss of electrons from the s and 3d orbital. The elements in this group can have different oxidation states, which makes them useful as catalysts.
Compounds of the transition elements can be paramagnetic (attracted by a magnetic field) or diamagnetic (not attracted by a magnetic field). Paramagnetic in the transition elements is caused by the presence of unpaired electrons in the d sub-orbital. Diamagnetism is characteristic of compounds where all the electrons are paired in the d sub-orbital. These elements are very hard, with high melting points and boiling points. Moving from left to right across the periodic table, the five d orbital become more filled. The d electrons are loosely bound, which contributes to the high electrical conductivity and malleability of the transition elements. The transition elements have low ionization energies.
They exhibit a wide range of or positively charged forms. The positive oxidation states allow transition elements to form many different ionic and partially ionic compounds. The formation of complexes causes the d orbital to split into two energy sublevels, which enables many of the complexes to absorb specific frequencies of light. Thus, the complexes form characteristic colored solutions and compounds. Complexation reactions sometimes enhance the relatively low solubility of some compounds.
Common properties of transition metals:-
Hardness, Density, Melting and Boiling Point
- Transition metals have smaller atomic volumes than Group I and II metals because additional electrons are being progressively added to the inner atomic orbitals resulting in stronger attraction to the nucleus.
- These atoms of smaller volume can pack together more closely resulting in higher densities and hardness.
- Closer packing results in stronger bonding so more energy is required to melt or boil transition metals.
Ionisation Energy and Chemical Reactivity
- The smaller atomic radii of transition metals means the valence shell (outer-shell) electrons are more strongly attracted to the nucleus and therefore less easily removed resulting in higher first ionisation energies compared to Group I and II metals.
- Because electrons are less easily lost, the transition metals are less chemically active than Group I and II metals.
- The lower chemical reactivity of the transition metals means they will be placed lower down in the activity series of metals compared to Group I and II metals.
- Since oxidation relates to the loss of electrons, transition metals are less easily oxidised than Group I and II metals.
Oxidation States
- The energies of the 3d and 4s orbital are very close.
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Often the lowest oxidation is +2 corresponding to the loss of 2 ns orbital electrons.
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Higher oxidation states correspond to the additional loss of (n-1)d orbital electrons.
- The decrease in maximum states after manganese in the first transition metal series (and after iridium in the second series and osmium in the third series) reflects the difficulty of breaking into a half-filled d sub shell.
Colored Compounds
- A substance will appear colored if it absorbs light from some portion of the visible spectrum.
- Ions with d orbital electrons appear colored because energy from visible light is absorbed and used to promote a d orbital electron to a higher energy d sublevel (referred to as d-d transitions).
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Ions with no d orbital electrons are colorless, e.g., Sc3+, Ti2+.
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Ions with d10 electron configurations are colorless, d-d transitions are impossible because the d orbital are all filled, e.g., Zn2+
Paramagnetism
- Paramagnetism is a weak attraction into a magnetic field.
- Substances with unpaired electrons can be paramagnetic.
- Paramagnetism is caused by both the orbital and spin motions of electrons (any rotating or revolving charged object generates a magnetic field).
- The magnetic fields of paired electrons cancel out, so only unpaired electrons contribute to paramagnetism.
Ferromagnetism
- Ferromagnetism is a strong attraction into a magnetic field.
- Ferromagnetism occurs when atoms with unpaired electron spins are just the right distance apart to permit the individual spins to align with each other within a relatively large region.
The individual spins within this region act cooperatively resulting in a large magnetic effect.
- Only solids can show ferromagnetism.
- The only ferromagnetic elements at room temperature are iron, cobalt and nickel.
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Ferromagnetic compounds such as CrO2 and Fe3O4 also exist.
CONCLUSION:
The 38 elements in groups 3 through 12 of the periodic table are called "transition metals". As with all metals, the transition elements are both ductile and malleable, and conduct electricity and heat. The interesting thing about transition metals is that their valence electrons, or the electrons they use to combine with other elements, are present in more than one shell. This is the reason why they often exhibit several common oxidation states. There are three noteworthy elements in the transition metals family. These elements are iron, cobalt, and nickel, and they are the only elements known to produce a magnetic field.
Transition metal generally shows:
-
higher
- higher melting and boiling points
- higher ionization energies
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a range of
- colors in their compounds
- the ability to form a wide range of coordination compounds
- paramagnetism (ability to attract a magnetic field)
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less chemical reactivity than and
POST LAB QUESTIONS:
- Describe the physical properties of transition metals.
Physical properties of transition metals are hard, dense and shiny. They are good conductors of heat and electricity. They are also malleable and ductile.
- How do transition metals react with water?
Transition metals react with water very slowly, if at all.
- What properties do the compounds of transition metals have in common?
The common properties, they form colored compounds. They form compounds that can have more than one formula.