Is hydrogen a group 1 element?

UserInvalid

Just like the title says :

"Is hydrogen a group 1 element? "

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Reply 1

Plato's Trousers

Original post by UserInvalid

Just like the title says :

"Is hydrogen a group 1 element? "

I would imagine they are asking for a discussion of hydrogen's chemical properties and therefore why it can be considered a group 1 element in some situations and not in others. This is why you sometimes see hydrogen "cut off" the top of group 1 and floating free from the rest of the table.

Think about what "group one-ness" means. Then think about whether hydrogen fits that. Then think about if and when hydrogen doesn't fit that. Then you will have your answer

Reply 2

UserInvalid

Original post by Plato's Trousers

I believe hydrogen is not alkali metal. So how can it belong to group 1?

Reply 3

Plato's Trousers

Original post by UserInvalid

I believe hydrogen is not alkali metal. So how can it belong to group 1?

you are right. hydrogen is not an alkali metal. However, it can be oxidised to a positive ion (just like an alkali metal). So in this sense, you could say it is in group 1. It also has one valence electron (again, just like an alkali metal)

however, there are other reactions which are not shared by the alkali metals. What are they?

(edited 12 years ago)

Reply 4

UserInvalid

Original post by Plato's Trousers

not sure which reactions they are.

But usually you see that hydrogen is seperated in from group one in the periodic table, what is the final conclusion made by the scientist about this?

Reply 5

Plato's Trousers

Original post by UserInvalid

not sure which reactions they are.

But usually you see that hydrogen is seperated in from group one in the periodic table, what is the final conclusion made by the scientist about this?

well, hydrogen can form covalent bonds (eg in water, methane etc). Alkali metals do not do this, so in this sense hydrogen is not in group 1

also, hydrogen can be reduced to form a negative ion (H^-) in compounds like sodium hydride (NaH). The alkali metals cannot do this. In this sense, hydrogen is more like a halogen and so you could say it is in group 7

So, hydrogen is basically an anomaly. It doesn't really fit in any of the groups properly.

Reply 6

thegodofgod

Original post by UserInvalid

not sure which reactions they are.

But usually you see that hydrogen is seperated in from group one in the periodic table, what is the final conclusion made by the scientist about this?

What's the oxidation state of hydrogen in LiAlH₄, lithium aluminium hydride: Li = +1, Al = +3.

Reply 7

UserInvalid

Original post by Plato's Trousers

well said. Did not got that on my head till you reminded me.

Therefore we can not claim hydrogen to be part of group 1 or being a part of group 1.

Original post by thegodofgod

What's the oxidation state of hydrogen in LiAlH₄, lithium aluminium hydride: Li = +1, Al = +3.

The oxidation number of hydrogen is -1 when it is combined with a metal if I may be right.

Reply 8

Plato's Trousers

Original post by UserInvalid

well said. Did not got that on my head till you reminded me.

Therefore we can not claim hydrogen to be part of group 1 or being a part of group 1.

you cannot claim it belongs solely to gp I, that's right. But it has some aspects of group I behaviour

Original post by UserInvalid

The oxidation number of hydrogen is -1 when it is combined with a metal if I may be right.

correct. As it is also in sodium hydride. this is more like group 7 behaviour

Reply 9

thegodofgod

Original post by Plato's Trousers

you cannot claim it belongs solely to gp I, that's right. But it has some aspects of group I behaviour

correct. As it is also in sodium hydride. this is more like group 7 behaviour

But am I right in saying that hydrogen hardly ever forms hydride ions - it's mostly just protons, right? :colondollar:

Reply 10

Plato's Trousers

Original post by thegodofgod

But am I right in saying that hydrogen hardly ever forms hydride ions - it's mostly just protons, right? :colondollar:

well, yes, you could say that. It only really forms hydride ions on Thursdays :biggrin:

(its electron affinity is way lower than that of the halogens)

Reply 11

thegodofgod

Original post by Plato's Trousers

well, yes, you could say that. It only really forms hydride ions on Thursdays :biggrin:

(its electron affinity is way lower than that of the halogens)

Also, to the OP, you could say that hydrogen's outer electrons aren't in the p sub-shell, unlike group 7 elements.

Reply 12

Plato's Trousers

Original post by thegodofgod

Also, to the OP, you could say that hydrogen's outer electrons aren't in the p sub-shell, unlike group 7 elements.

correct. in fact the lack of anything other than s-orbitals is the key to hydrogen's odd-ness. No other element has that (well apart from He, but that doesn't do any chemistry)

Reply 13

thegodofgod

Original post by Plato's Trousers

correct. in fact the lack of anything other than s-orbitals is the key to hydrogen's odd-ness. No other element has that (well apart from He, but that doesn't do any chemistry)

Also, I'm not sure whether this is what is meant by alkali metals,

but hydrogen's hydroxide (water) is neutral, but group 1 hydroxides are basic, but I don't think group 7 hydroxides exist :moon:

Reply 14

Plato's Trousers

Original post by thegodofgod

Also, I'm not sure whether this is what is meant by alkali metals,

but hydrogen's hydroxide (water) is neutral, but group 1 hydroxides are basic, but I don't think group 7 hydroxides exist :moon:

exactly right. that's why they are called alkali metals.

(you could claim that chloric (I) acid is a group 7 hydroxide, I guess... but not an ionic one)

Reply 15

thegodofgod

Original post by Plato's Trousers

exactly right. that's why they are called alkali metals.

(you could claim that chloric (I) acid is a group 7 hydroxide, I guess... but not an ionic one)

Ahh - is that the conjugate acid of sodium hypochlorite found in bleach: NaClO

Reply 16

Plato's Trousers

Original post by thegodofgod

Ahh - is that the conjugate acid of sodium hypochlorite found in bleach: NaClO

indeed it is. HOCl

The Cl is on oxidation state +1 so you could say it's a hydroxide of chlorine, I guess, by analogy with NaOH (where the sodium is in oxidation state +1).

However, HOCl is covalent... so not really..

Reply 17

AkDo

Original post by UserInvalid

Just like the title says :

"Is hydrogen a group 1 element? "

It shares properties of an alkali metal in that it makes hydrogen hydroxide (water) but it shares properties of other groups as it can share electrons like in water again or form a diatomic molecule like the halogens

Reply 18

UserInvalid

we can claim that it shares some properties, just like transition metals which share similar properties like alkali metals in a way of conducting electricity e.t.c

we can not say transition elements are in group 1, they are seperated out despite having similar properties.

So what can we say about hydrogen? it is sharing similar properties from group 1 till 7, I would say it is a part of its own group.

This is quite confusing, lets hear what others say.

Reply 19

Red_Inferno112

Honestly, going by principle, hydrogen should be in Group 1, above lithium.

This is because its outer shell is the same (s1), halogens all have the outer config of (xs2 xp5).
Furthermore, although it seems strange, it is chemically similar to the alkali metals. Even though we think of it as a covalent bond-forming gas, it only has a Pauling Electronegativity of ~2.2, compared to carbon of ~2.5, lithium of ~1, sodium of ~<1, fluorine of ~4, chlorine of ~3. In terms of a consistent fall in electronegativity, it does not fit in with the halogens (All stable ones are actually more electronegative than hydrogen). It does with the Alkali metals though.

Furthermore, under pressure, hydrogen is indeed metallic.

Very unique element, but the only reason I can think to leave it out is to glorify it being the lightest (first) element.