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1.	State the Physical properties of alkali metals. Explain.
Answer» Physical properties: (a) Large atomic radii: The atomic radii of alkali metals are the largest in their respective periods. These increase as we travel down the group. (b) Large ionic radii: The ionic radii increase as we move down the group due to the addition of a new energy shell with each succeeding element. (c) Low ionization enthalpy: The ionization enthalpies decrease as we move down the group.The ionization enthalpies of the alkali metals are the lowest due to loosely held s- electron. (d) Hydration enthalpy: It decreases with the increase in ionic radii.The hydration enthalpy of Li ion is the maximum and the hydration enthalpy of Cs ion is the minimum. (e) Oxidation state: The alkali metals exhibit oxidation state of +1 in their compounds and are strongly electropositive in character. The electropositive character increases from Li to Cs. (f) Metallic character: The metallic character increases down the group. (g) Melting point and boiling point: The m.p and b.p of alkali metals are very low and decrease with increase in atomic number. (h) Nature of bonds formed: These metals form ionic bonds. The ionic character increases as we down the group. (i) Flame colouration: All the alkali metals impart a charactersistic colour to the flame. (j) Photoelectric effect: Alkali metals (except Li) exhibits photoelectric effect.

State the Physical properties of alkali metals. Explain.

Answer»

Physical properties:

(a) Large atomic radii: The atomic radii of alkali metals are the largest in their respective periods. These increase as we travel down the group.

(b) Large ionic radii: The ionic radii increase as we move down the group due to the addition of a new energy shell with each succeeding element.

(c) Low ionization enthalpy: The ionization enthalpies decrease as we move down the group.The ionization enthalpies of the alkali metals are the lowest due to loosely held s- electron.

(d) Hydration enthalpy: It decreases with the increase in ionic radii.The hydration enthalpy of Li ion is the maximum and the hydration enthalpy of Cs ion is the minimum.

(e) Oxidation state: The alkali metals exhibit oxidation state of +1 in their compounds and are strongly electropositive in character. The electropositive character increases from Li to Cs.

(f) Metallic character: The metallic character increases down the group.

(g) Melting point and boiling point: The m.p and b.p of alkali metals are very low and decrease with increase in atomic number.

(h) Nature of bonds formed: These metals form ionic bonds. The ionic character increases as we down the group.

(i) Flame colouration: All the alkali metals impart a charactersistic colour to the flame.

(j) Photoelectric effect: Alkali metals (except Li) exhibits photoelectric effect.

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