# Which metals are "heavy"? **URL:** \ **Category:** Factual Questions\ **Created:** [June 14, 2004, 5:02pm UTC](https://boards.straightdope.com/t/which-metals-are-heavy/250308 "2004-06-14T17:02:58Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Da\_Cissy\_Pimp](https://avatars.discourse-cdn.com/v4/letter/d/4af34b/32.png) [@Da\_Cissy\_Pimp](https://boards.straightdope.com/u/Da_Cissy_Pimp)\ **Post date:** [June 14, 2004, 5:02pm UTC](https://boards.straightdope.com/t/which-metals-are-heavy/250308/1 "2004-06-14T17:02:58Z")
Often I hear mention made of so-called “heavy metals”: metals that it is considered a bad idea to get into one’s body. So which metals fall into this category? Lead, mercury and cadmium are the three that I seem to hear mentioned the most, but I have heard that there are others as well. What determines whether a metal is “heavy” or not? Do the heavy metals all have some chemical property (or properties) in common, or are they designated as such simply due to their toxicity (or is it a bit of both: their toxicity being due to some chemical property they all have)? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [June 14, 2004, 5:11pm UTC](https://boards.straightdope.com/t/which-metals-are-heavy/250308/2 "2004-06-14T17:11:34Z")
There are a wide range of [definitions](http://www.webref.org/chemistry/h/heavy_metal.htm), depending on the properties one wishes to group them by. ---
**Author:** ![erislover](https://avatars.discourse-cdn.com/v4/letter/e/71e660/32.png) [@erislover](https://boards.straightdope.com/u/erislover)\ **Post date:** [June 14, 2004, 5:16pm UTC](https://boards.straightdope.com/t/which-metals-are-heavy/250308/3 "2004-06-14T17:16:59Z")
> [@](#): > > When speaking of heavy metals we generally mean, lead, mercury, iron, copper, manganese, cadmium, arsenic, nickel, aluminum, silver, and beryllium. [Link](http://www.luminet.net/~wenonah/hydro/heavmet.htm). As QED notes, I don’t believe there is a hard-and-fast definition. Zinc is common for bird poisoning. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [June 14, 2004, 5:19pm UTC](https://boards.straightdope.com/t/which-metals-are-heavy/250308/4 "2004-06-14T17:19:24Z")
Well, they’re heavy. That may sound like a flip answer, but one definition (Webster’s dictionary) is “metals with a specific gravity greater than 5g/cm[sup]3[/sup]”. However, as I remember from my chemistry classes, they are the transition metals in rows 4 and below.[Cite](http://jchemed.chem.wisc.edu/Journal/Issues/1997/Nov/abs1374.html). Actually, that cite indicates that the post-transition metals, up to group 16, are also included. By that definition, and looking at the [url=]periodic table, you have the elements coloured pink from 21 (scandium) down to 80 (mercury), and the first four of the orange-coloured ones after each of these rows (Ga-Se, In-Te, and Tl-Po). ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [June 14, 2004, 5:20pm UTC](https://boards.straightdope.com/t/which-metals-are-heavy/250308/5 "2004-06-14T17:20:03Z")
> [@erislover](#): > > I don’t believe there is a hard-and-fast definition. It seems you’re not alone, either. From the bottom of my linked page: > [@](#): > > The term “heavy metal” has never been defined by any authoritative body such as IUPAC. Over the 60 years or so in which it has been used in chemistry, it has been given such a wide range of meanings by different authors that it is effectively meaningless. No relationship can be found between density (specific gravity) or any of the other physicochemical concepts that have been used to define heavy metals and the toxicity or ecotoxicity attributed to heavy metals. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [June 14, 2004, 5:28pm UTC](https://boards.straightdope.com/t/which-metals-are-heavy/250308/6 "2004-06-14T17:28:25Z")
Sorry, a bit more I should have added: > [@Da Cissy Pimp](#): > > Do the heavy metals all have some chemical property (or properties) in common, or are they designated as such simply due to their toxicity (or is it a bit of both: their toxicity being due to some chemical property they all have)? It’s both. Most of the heavy metals are [transition metals](http://www.wordiq.com/definition/Transition_metal), i.e. they have partially filled _d_-orbitals. They are therefore very good at forming “complexes” with organic compounds. This is useful in the body in the right place - e.g. haemoglobin is a complex of iron with a protein molecule - but also means that heavy metals can bind to proteins that they shouldn’t, which is why they are toxic. See here: [http://www.luminet.net/~wenonah/hydro/heavmet.htm](http://www.luminet.net/~wenonah/hydro/heavmet.htm)