Question

Explain the following
A. Hydrogen shows similarity with alkali
metals as well as halogens.​

Answer 1

Similarities to Halogens

Noble Gas Configuration: Hydrogen can gain one electron to complete its valence shells. Halogens also have seven electrons in their last shell and can gain one electron to gain noble gas configuration.
Electronegativity: They also share the same electronegative nature. Hydrogen also gains one electron (not looses) to become stable and so do halogens.
H + e‾ → H‾

Cl + e‾ → Cl‾

Diatomic Molecules: Both hydrogen and halogens form diatomic molecules. Hydrogen forms H2 and, halogens are Cl2, F2 etc
Reaction with Metals: Hydrogen combines with metals to form metallic hydrides. Similarly, halogens also combine with metals to form metal halides.
2Na + H2 → 2NaH

Ca + H2 → CaH2

Covalent Bonding: Halogens and hydrogen both also combine with non-metals to form molecules with covalent bonding.
Differences with Halogens

Structure of Atom: Hydrogen has only one electron in its outer shell. All halogens have seven electrons in their last shell
Size of Atom: The size of the H- ion is much larger than those of the ions of Halogens. This is because hydrogen has only one electron and proton and the pull of the nucleus is less.
Reaction with Water: Also unlike halogens, the hydrogen ion H- is unstable in water.

Answer 2

Answer:

(1) Hydrogen shows similarity with alkali metals :

(i) Hydrogen has electronic configuration 1s¹ which is similar to outer electronic configuration of alkali metals, ns¹.

(ii) Both, hydrogen and Alkali metals form univalent positive ions (+1) by loss of 1 electron

(iii) Both combine with halogen to form halides.

$\sf{H_2 + Cl_2 → 2HCl}$

$\sf{2Na + Cl_2 → 2NaCl.}$

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(2) Hydrogen show similarity with halogens :

(i) Halogens have outer electronic configuration $\sf{ns^2np^5}$ which resembles that of hydrogen 1s¹.

(ii) Both form univalent negative ion (-1).

(iii) Both react with metals.

$\sf{2Na_{(s)} + H_2{(g)}→2NaH_{(s)}}$

$\sf{2Na + Cl_2 →2NaCl}$