Talk:Formula unit

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What is the value for a formula unit?

the unit of a formula —Preceding unsigned comment added by 98.28.189.157 (talk) 03:47, 7 August 2008 (UTC)

It's the number of molecules with in a specified weight. Grams of known species divided by molecular weight of species times Avogadro's number. -University of Idaho Chemistry Undergrad —Preceding unsigned comment added by 129.101.117.227 (talk • contribs) 03:04, 12 December 2008

Its value is two-fold: 1) For use in stoichiometric calculations; and 2) For practicality. Using sodium chloride as an example: you have a crystal of sodium chloride, all ions are electrostatically bonded to six surrounding oppositely charged ions, so that the whole crystal is one large bonded single unit--you would have to express its formula as (for example) Na_{250282001912532}Cl_{250282001912532}, which not only is awkward, but it is impossible to know the exact amount of bonded ions in any one particular crystal. The empirical formula (formula unit) seems a bit of an easier way to express it: NaCl, the lowest whole number ratio, which here is 1:1. The same goes for any other ionic crystal. For example, the crystal of a 1:2 ratio compound such as MgCl₂ might have formula of Mg_143204113Cl_286408226, which again would be awkward and impossible to determine, so MgCl₂ represents the crystal. If you want a more specific expression of the size of the crystal, you could say X grams of NaCl or X grams of MgCl₂. Zomax7000 (talk) 15:42, 23 May 2010 (UTC)Joel Weiner, HS chem teacher —Preceding unsigned comment added by Zomax7000 (talk • contribs) 23:26, 18 May 2010 (UTC)

Is defining the formula unit as an "empirical formula" not problematic? Empirical formula focuses on the smallest whole number ratio of atoms for each element in the sample, rather than smallest whole number ratio of ions. For example, the formula unit of sodium oxalate is Na₂C₂O₄. Would the empirical formula of sodium oxalate not then be different (NaCO₂)? — Preceding unsigned comment added by 209.184.113.119 (talk) 02:16, 19 June 2019 (UTC)

they've defined empirical formula wrong in this article by saying ions. They got empirical formula right in their empirical formula page by saying atoms https://en.wikipedia.org/wiki/Empirical_formula "In chemistry, the empirical formula of a chemical compound is the simplest whole number ratio of atoms present in a compound"

And besides that, they're still wrong in this article on formula unit, because the formula unit isn't the same or isn't necessarily the same, as the empirical formula! Consider these ionic compounds Hg2N2O6 or K2S2O8 check them on pubchem, (what they call the molecular formula for those ionic compounds, is the formula unit). The empirical formula, lowest ratio of atoms, would be eg KSO4 whereas the formula unit (or perhaps should say formula for formula unit?) is K2S2O8

also

https://media.iupac.org/publications/analytical_compendium/Cha01sec37.pdf

A formula unit is not a unit but an entity specified as a group of atoms by the way the

chemical formula is written. 86.1.49.43 (talk) 05:44, 10 December 2022 (UTC)

Here's another error in the wikipedia definition here.. Besides that they're trying to say formula unit is empirical formula for ionic compounds. They've then gone on to try to give a definition of empirical formula as "It is the lowest whole number ratio of ions represented in an ionic compound." And besides the ions/atoms issue. Another issue is what on earth does "lowest whole number ratio" mean. The ratio isn't meant to be made higher or lower. Just simplified.

They don't mess up their definition of empirical formula on their empirical formula page. On their empirical formula page they say "In chemistry, the empirical formula of a chemical compound is the simplest whole number ratio of atoms present in a compound. A simple example of this concept is that the empirical formula of sulfur monoxide, or SO, would simply be SO, as is the empirical formula of disulfur dioxide, S2O2."

See they say "simplest whole number" not "lowest whole number".

Also, as for their mention in the formula unit page, of ions rather than atoms.. That doesn't work well, because if an ion is polyatomic then the only way you can even show ions is with a condensed structural formula. An empirical formula doesn't even necessarily show ions. And if a formula is required to show the ions, it could be showing atoms in parentheses with a subscript outside the parenthesis. That's not simplest ratio of atoms. For that it'd have to at least show each atom and its subscript, and no parentheses. 86.1.49.43 (talk) 23:41, 10 December 2022 (UTC)

Chemistry

Unit cell chemistry 2409:4081:1C05:86D3:0:0:EA08:8E00 (talk) 16:20, 27 February 2024 (UTC)

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formula unit all relationships

2404:3100:1C10:8048:4289:4C7C:9319:45F9 (talk) 05:33, 30 May 2024 (UTC)