Question

Give reasons for the following:
(i) Sodium is more reactive than aluminium.
(ii) Mercury is not the only metallic liquid at around 30 C.
(iii) Metals always combine by electrovalency.
(iv) Metal ions are always positively charged.
(v) Metal ions always get discharged at the cathode during electrolysis.
(vi) Metals generally do not form hydrides.
(vii) Metals are always monoatomic.
(viii) Sodium and potassium cannot be kept exposed to air.
(ix) Sodium and potassium should not be treated with acids.
(x) Hydrogen is not a metal but it has been assigned a place in the reactivity series of metals.

Answer 1

(i) Sodium loses electrons more easily as compared to aluminium and forms cations. Thus, sodium is more reactive than aluminium.

(ii) The melting point of gallium and cesium is below ${30}^{\mathrm{o}}\mathrm{C}$. Thus, around ​${30}^{\mathrm{o}}\mathrm{C}$, gallium and cesium exist in the liquid form.

(iii) Metals usually have 1, 2 or 3 valence electrons. It is easy for these metals to lose electrons and attain the inert gas configuration. They donate electrons to non-metals, which require these electrons to attain a stable configuration. Thus, metals always form bonds with non-metals by the transfer of electrons (electrovalency).

(iv) Metals usually have 1, 2 or 3 valence electrons. They get ionised by losing electrons, thus, forming positively charged ions (cations).

(v) As metals always lose electrons and form positively charged ions (cations), they are electropositive in nature. So, these electropositive metal ions move towards the oppositely charged negative electrode (cathode) and discharge there.

(vi) Metal hydrides formed by metals and hydrogen are highly unstable. Thus, metals generally do not form hydrides.

(vii) Metals form compounds by transferring electrons to electron deficient elements (non metals). They cannot attain stability by sharing electrons. Thus, they are always monoatomic.

(viii) Sodium and potassium are highly reactive metals and are placed at the top of the reactivity series. When exposed to air, they react readily and get oxidised to form the respective oxides. They do not react with kerosene. Due to their highly reactive nature, both sodium and potassium are stored in kerosene.

(ix) Sodium and potassium ​react violently with dilute acids and release hydrogen gas. Thus, they should not be treated with acids.

(x) Similar to metals, hydrogen also loses an electron to form ${\mathrm{H}}^{+}$ ion. Therefore, although hydrogen is not a metal, it has been assigned a place in the reactivity series.