Explanation
A metallic solid or liquid that is composed of a homgeneous mixture of two or more metals or of metals and non-metals or metalloid elements, usually for the purpose of imparting or increasing specific characteristics or properties.
Mercury doesnot react with iron.Hence iron and mercury cannot form an alloy.
Electrons exchange orbitals in order to stabilizes themselves. The energy released is called exchange energy and it depends on how many electrons are occupied in the orbitals plus their symmetrical distribution. Half filled and full filled subshells provide more stabilization (more exchange energy) due to their symmetrical nature.
Hence the six unpaired electrons present in f-shell can exchange 15 electrons.
The lanthanoid which exhibits + 4 oxidation is Cerium
The lanthanide and actinide series make up the inner transition metals. The lanthanide series includes elements 58 to 71, which fill their 4f sublevel progressively. The actinides are elements 89 to 103 and fill their 5f sublevel progressively. Actinides are typical metals and have properties of both the d-block and the f-block elements, but they are also radioactive. Lanthanides have different chemistry from transition metals because their 4f orbitals are shielded from the atom’s environment.
The common oxidation state of lanthanoids is +3. Some of the lanthanoids may also shows +2 and +4 oxidation states, however they more easily revert to the more stable +3 state.
Actinides are typical metals and have properties of both the d- and f-block elements and also they are radioactive . Where as in lanthanides, except promethium , all are non-radio active.
In compounds of cerium, the most common oxidation states of cerium are +3 and +4.
4f and 5f belongs to different energy levels. Hence the shielding effect on them is not the same. Shielding effect of 4f is more than 5f.
Because actinides are bigger, the outer most shell is further away from the nucleus that means the ionization energy is lower for the corresponding oxidation state compared lanthanides.
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