Question

why hydrogen cannot Placed in group 1A and 7A of the periodic table
write atleast four points​

Answer 1

Answer:

The reason why the hydrogen can be placed in both group 1 and group 17 is that it resembles Alkali metals in some of its properties like it can easily form cations so, it can be placed in Group 1 of periodic table but it also resembles Halogens in its properties like it forms  which is true property of halogen that is why it can be placed in group 17 of periodic table. As hydrogen can accept as well has the tendency to reject electron to make itself stable. It is the smallest member of the family.

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Answer 2

The resemblance of hydrogen with alkali metals (Group -1):

1. Electronic configuration:- like alkali metals hydrogen also contains one electron in its outermost shell. Example: H-1, Li-2,1

2. Electropositive character:- like alkali metals ($Na^+, K^+$) hydrogen also loses its only one electron to form hydrogen ion, $H^+$

3. Oxidation state:-like alkali metals hydrogen exhibits an oxidation state of +1 in its compounds. Example $=HCl, NaCl$

4. Combination with non-metals:- like alkali metals hydrogen combines with non-metals such as oxygen and sulphur forming their oxides and sulphides. Example- $H_2$ Olike $Na_2, K_2 O$

5. Like alkali metals hydrogen also act as a strong reducing agent.

The resemblance of hydrogen with halogens (Group -17):

1. Electronic configuration:- All halogens have 7 electrons in their respective outermost shell and thus have one less electron than the stable configuration of nearest noble gas Hydrogen on the other hand has one electron less than the stable configuration of nearest noble gas i.e. Helium

2. Electronegative character:-Halogens have a strong tendency to gain one electron to form halide ions, In a similar way hydrogen shows some tendency to gain one electron to form hydride ion.

3. Oxidation state:- Just like halogens hydrogen shows an oxidation state of -1. Like halogens, hydrogen easily combines with nonmetals such as carbon, silicon,nitrogen, etc to form covalent compounds.Examples: $CH_4$

Thus, it can be placed both in group 1 and group 17.

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