Why actinides and lanthanides series are kept in the bottom of the periodic table? Reasons? Thank you.

Answer 1

This is a consequence of electronic structure........

The #"lanthanides"# and #"actinides"# each show progressive filling of the #f-"orbitals"#. We know that the filling of the #d-"orbitals"# gives rise to peculiar chemistry in the transition series, given the geometric properties of the #d-"orbitals"#. The #f-"orbitals"# are multi-lobed, and they are very poorly shielded from the nuclear charge.
And thus #f-"orbital"# electrons do not tend to participate in bonding because they are too tightly held by the nuclear charge. The result is that the lanthanides tend to lose the 2 or 3 valence electrons in the s shell, and form a series of #M^(3+)# cations (or more rarely #M^(2+)# cations). Lanthanides and actinides thus tend to have a particular chemistry which is exclusive to themselves. Most lanthanide chemists also study the chemistry of scandium and yttrium, which as #M^(3+)# and #M^(2+)#, very potent Lewis acids, have a parallel and complementary chemistry.
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Answer 2

Since the actinides and lanthanides series are both defined by inner electron shell filling, they are positioned below the main body of the periodic table to prevent it from becoming unduly wide. These elements also share similar chemical properties within their respective series, which further supports their placement below the main table to preserve the periodicity of the elements.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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