Identify the element one that does NOT belong to Group 1 of the Modern Periodic Table.

Question

Question

This question was previously asked in

SSC CGL 2023 Tier-I Official Paper (Held On: 17 Jul 2023 Shift 3)

Answer 1

The correct answer is Hydrogen .Key Points

Although hydrogen is located in the same group (Group 1) as the alkali metals in the modern periodic table, it does not share all the typical properties of the alkali metals, and is therefore often not considered part of this group.
Hydrogen is unique because, despite being placed above the alkali metals (lithium, sodium, potassium, rubidium, cesium, and francium) in the periodic table, it is not a metal, but a non-metal. Hydrogen also forms diatomic molecules (H₂), while alkali metals do not.
Furthermore, hydrogen's electron configuration is unique — it has only one electron in its outer energy level, whereas alkali metals have a single electron in their outermost energy level, but also have filled inner energy levels.

Additional Information

Hydrogen forms a positive ion (H+) by losing one electron, similar to alkali metals. But unlike alkali metals, hydrogen can also form a negative ion (H-) by gaining one electron, which makes it unique.
Alkali metals are highly reactive due to their tendency to lose their outermost electron to achieve stability, while hydrogen is fairly reactive but to a lesser extent.
Alkali metals react violently with water to form hydroxide ions and hydrogen gas. Hydrogen, on the other hand, can form water by reacting with oxygen.
Hydrogen has three isotopes: Protium (1H), Deuterium (2H), and Tritium (3H). No alkali metal showcases this kind of isotopic variety.
Hydrogen can exist as a gas, liquid, or a solid under different conditions, whereas Group 1 elements are all solid at room temperature.
Hydrogen can bond with many non-metal elements to form covalent bonds. This is not true of alkali metals which typically form ionic bonds.
In terms of its placement in the periodic table, hydrogen is sometimes also put in Group 17 with the halogens, due to its ability to gain an electron to achieve a full outer shell, similar to the halogens.