Wikipedia:Reference desk/Archives/Science/2021 May 31

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May 31

Equivalence concept vs Mole concept

What is the need for Mole concept when there is already an equivalence mass concept in Chemistry ? Signed by Kiddo Learner talk at 05:46, 31 May 2021‎.

I quote from equivalent weight: "These values correspond to the atomic weight divided by the usual valence", whereas mole is independent of charge. Sometimes charge is important, such as the mentioned acid-base reactions mentioned in the article, but more often than not, it isn't, and using equivalent weight would just be a unnecessary headache. The two are related but not interchangeable in many situations. Fgf10 (talk) 15:12, 31 May 2021 (UTC)

You might also like to read Mole (unit), which is based on Avogadro's number, Kiddo Learner. The mole is one of the basic units of the SI system, whereas "equivalence" is a relative term that depends on the outcome of the reaction, which the experimentalist may not know at the outset — so, for example one could react chlorine with benzene and get different results according to the relative amounts used. Mike Turnbull (talk) 15:42, 31 May 2021 (UTC)

As noted above, equivalence is only useful in situations with ionic compounds and acids and bases, and with chemical reactions of the same, you most often see it in Equivalent concentration calculations, but even today, it's largely not used anymore. The mole is a much more generalizable concept and works in a wider variety of reactions. Indeed, as taught in most chemistry curricula today, normality and equivalence is seen as an extra and unnecessary step over simple molar calculations. --Jayron32 13:17, 1 June 2021 (UTC)

Einsteinium the last element to have a compound?

It doesn't seem that Fermium has a compound but Einsteinium's page doesn't say anything about it being the last one to have one. Is it? UB Blacephalon (talk) 21:38, 31 May 2021 (UTC)

This question has already been answered, I think adequately, at the Teahouse.--Shantavira|^{feed me} 07:39, 1 June 2021 (UTC)

but only at 23:31, 31 May 2021 (UTC), after poster had been told over there to go here with their question.  --Lambiam 08:13, 1 June 2021 (UTC)

As the article Nobelium#Chemical mentions, even synthetic elements have compounds. Nobelium chloride was made as long ago as 1967, together with fermium chloride. There would be no point claiming some element was the "last one" to have a compound, as all elements have (in theory) compounds: they have just not all been available to experiments, given the limited quantity of material available. Mike Turnbull (talk) 09:54, 1 June 2021 (UTC)

There may be gaps in the ability of transuranium elements to form compounds. Oganesson "should" be a noble gas, based on its position in the periodic table, but it may be a solid under normal conditions, and it may be too reactive to be considered noble. At the moment, nothing much is certain. But in any case its successor, ununennium, should be highly reactive.  --Lambiam 21:30, 1 June 2021 (UTC)

@Lambiam: Late, but couldn't resist noticing this. :) The textbook diagonal "metalloid line" would actually reach elements 117 and 118 in the seventh period. Relativistic effects for late p-elements help to enhance metallisation (Po is much more clearly metallic than Sb is; At likely manages to form a metallic structure despite being on the wrong side of the line, though chemically it is a very bad metal); they must be very strong here, because they go like the 4th power of the atomic number IIRC. (Underlying reason being p_3/2 expansion, giving large atomic radius and low ionisation energy.) So it's actually not totally far-fetched that element 118 is a metal in the noble gas group(!), though probably a pretty poor one if so, like tin. Double sharp (talk) 15:23, 27 March 2022 (UTC)