Chemistry Chapter on Alkali and Alkaline Earth Metals

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Study Notes

Outer electronic configuration: ns1 for alkali metals and ns2 for alkaline earth metals.
Characteristics: Soft metals, low melting and boiling points, high reactivity due to low ionization enthalpy, and strong reducing agents.
Common oxidation states: +1 for alkali metals and +2 for alkaline earth metals.
Reactivity increases down the group; most form ionic compounds, except lithium and beryllium.

Consist of elements in groups 13 to 18, with the outermost electronic configuration ranging from ns2np1 to ns2np6.
Includes metals (e.g., tin, lead) and nonmetals (e.g., carbon, nitrogen).
Nonmetallic character increases left to right across periods; metallic character increases top to bottom within groups.
Higher ionization enthalpies than s-block elements.
Group 18 elements (noble gases) have stable configurations (ns2np6) and exhibit very low reactivity.
Halogens (group 17, ns2np5) and chalcogens (group 16, ns2np4) have highly negative electron gain enthalpies, gaining one or two electrons respectively to achieve stability.
Some elements exhibit multiple oxidation states.

Comprised of groups 3 to 12 with outer electronic configuration (n-1)d1–10ns0–2.
Mostly metallic, high melting and boiling points, form colored complexes, variable valency, and are often paramagnetic.
Notable elements acting as catalysts include Mn, Ni, Co, Cr, V, and Pt.
Classified as transition elements, bridging highly reactive s-block elements to less reactive p-block elements.

Positioned below the main periodic table and characterized by the entry of electrons into f-orbitals, denoted as (n-2)f1–14(n-1)d0or1ns2.
Includes lanthanoids (Ce to Lu, Z=58 to 71) termed rare earth elements, and actinides which start from Actinium (Z=89) to Lawrencium (Z=103).

Cation size decreases as effective nuclear charge increases, leading to reduced electron-electron repulsion.
Example: Formation of Li+ reduces the size from 123 pm to 60 pm.
Anion size increases with more electrons due to increased inter-electronic repulsion.

Ionization enthalpy is larger than ionization energy by a small margin (≈ 6 kJ/mol) and often considered negligible.
Alkali metals have low ionization enthalpies due to single valence electrons easily lost for stability.
Noble gases have high ionization enthalpies due to their stable electronic configurations.

Defined as the energy change when an electron is added to a gaseous atom forming an anion.
NEG (electron gain enthalpy): if energy is released during electron addition, it is negative; if energy is absorbed, it is positive.
Electron gain enthalpies are expressed in kJ/mol or eV.
Positive electron affinity means the resulting anion has lower energy than the neutral atom.