All alkali metals are solids hur hydrogen is a gas with diatomie
molecules Do you justify the inclusion of hydrogen in first group with
alkall metals
Answers
Hydrogen as alkali metal?
The only thing hydrogen has in common with alkali metals is in having one electron in its outermost shell and having a valency (combining power) of one. Unlike the group one elements hydrogen is clearly not a metal (it is a gas at room temperature) and is a poor conductor of heat and electricity. It does not readily form H+ cations and forms covalent bonds in most compounds, whereas group 1 metals readily form cations and form only ionic bonds. Also, alkali metals form basic oxides while hydrogen oxide (water) is amphoteric (both acidic and basic).
Hydrogen as a halogen?
Hydrogen, like the halogens, has one electron short of a complete outer shell and can form H- ions like Cl- and therefore forms ionic compounds with reactive metals – NaH similar in structure to NaCl. Hydrogen also exists as a diatomic gas like fluorine and chlorine. However, here the similarity ends – hydrogen is a reducing agent while the halogens are oxidising agents, hydrogen reacts vigorously with oxygen but not with most metals while the reverse is true of the halogens. Furthermore, hydrogen oxide (water) is amphoteric, while halogen oxides are acidic only.
So hydrogen is neither an alkali metal nor halogen.
Position Of Hydrogen
1)Hydrogen is the first element in the periodic table.
2)It is the lightest element known.
3)It atomic form exists only at high temperature.
4)It exist as a diatomic molecule i.e. H2 .That is why it is also called dihydrogen.
5) It was discovered by Henry Cavendish in 1766.
6) Its electronic configuration is 1s1
Unique position of Hydrogen in periodic table
A proper position could not be assigned to it because of the following reason:
1) In some properties it resembles alkali such, it can be placed in group 1 of the periodic table along with alkali metals.
2) In some other properties, hydrogen resembles such, it can be placed in group 17 along with halogens.
3) In some hydrogen differs from both alkali metals and halogens.
Resemblance with alkali metals
Hydrogen resembles alkali metals i.e. Li , K , Na , K, Rb ,Cs and Fr of group 1 of the periodic table.
1) Electronic configuration : Like alkali metals, hydrogen also contains 1 electron in its outermost shell.
Hydrogen 1s1
Lithium 1s2 2s1
Sodium 1s2 2s2 2p6 3s1
2) Electropositive character: Like alkali metals ,hydrogen also loses its only electron to form hydrogen ion i.e. H+
H ——-> H+ + e‾
Na ———-> Na+ + e‾
Hydrogen like alkali metals exhibit electropositive character.