Mention the general trends in group I with increasing atomic number (down the group) with respect to : (i) Atomic radius (ii) Ionisation enthalpy (iii) Flame colouration (iv) Basic nature of their oxides and hydroxides **OR** Describe Down's process for the preparation of sodiu

Question

Mention the general trends in group I with increasing atomic number (down the group) with respect to : (i) Atomic radius (ii) Ionisation enthalpy (iii) Flame colouration (iv) Basic nature of their oxides and hydroxides  **OR**  Describe Down's process for the preparation of sodium.

Accepted Answer

> > [!TLDR] > Down Group 1 (alkali metals): atomic radius increases, ionisation enthalpy decreases, each element continues to show a characteristic (though different) flame colour, and the basic character of oxides/hydroxides increases. > > (i) **Atomic radius:** Atomic radius increases steadily down Group 1 (Li < Na < K < Rb < Cs), because a new principal electron shell is added at each successive element, increasing the overall size of the atom despite the increasing nuclear charge. > > (ii) **Ionisation enthalpy:** Ionisation enthalpy decreases down the group (Li has the highest, Cs has the lowest, among naturally occurring alkali metals). As atomic size increases and the outermost (ns^1) electron is progressively farther from the nucleus and more shielded by inner electrons, it becomes easier to remove, so less energy is required. > > (iii) **Flame colouration:** All alkali metals impart a characteristic colour to a flame, because their very low ionisation enthalpy allows the outer electron to be thermally excited easily; each element's colour is specific to its own electronic transitions (Li = crimson red, Na = golden yellow, K = lilac/violet, Rb = red-violet, Cs = blue). Down the group, since ionisation enthalpy keeps decreasing, the outer electron becomes progressively easier to excite, but the property of showing a bright, characteristic flame colour is maintained throughout the group (only the specific colour changes from element to element). > …

Q.Mention the general trends in group I with increasing atomic number (down the group) with respect to :

Concept understanding — Alkali Metals — General Characteristics

Q.Mention the general trends in group I with increasing atomic number (down the group) with respect to :

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