Wikipedia:Reference desk/Archives/Science/2024 January 31

= January 31 =

Actual drawing of the Pentalobe screw profile
Hi. While repairing some electronics, I came across the Pentalobe screw. I noticed that Wikipedia, and many other sites, use a black-and-white generalized image to represent the Pentalobe screw profile. This image is made using 5 circles, with each circle's centre located at one vertices of a regular pentagon.

I don't know whether it's an optical illusion or not, but this "5 circles diagram" looks vastly different than the actual profile of the Pentalobe screw. It's more apparent if you look at a zoomed in image of the screw or screwdriver.

If the Pentalobe screw profile is indeed different than the "5 circles diagram", is there somewhere that I can find this profile?

Anything would be extremely helpful, even non-official sources, because right now the best thing I found is just a zoomed in image of a screwdriver tip, which is less than ideal. Liberté2 (talk) 02:41, 31 January 2024 (UTC)
 * c:Category:Pentalobe screws has photos and diagrams of several different variations. One important variable is the size of the circle relative to the pentagon. If the circles are tangent to each other or overlap, there is a point where they meet, like File:Pentalobular.svg. If the circles are small enough that they don't touch, like File:Medida de un tornillo pentalobular.svg, what should be the profile in the space between them? A second is an apparent difference of design: starting with a circular hole, do the five circles expand it (bumped-out curves) like File:Pentalobular.svg, or contract it (bumped-in) like File:Torx plus tamper.jpg? Is there an overlap of terminology between 'pentalobe' and 'torx variant with 5 points'? DMacks (talk) 09:56, 31 January 2024 (UTC)
 * The shape of the indentation of (Apple-specs conforming) Pentalobe screws should be more determinative than the heads of some screwdrivers capable of turning them. As seen here for bottom case screws of a MacBook, the circles clearly overlap. --Lambiam 10:26, 31 January 2024 (UTC)

Are free radicals electrophile?
Are free neutral radicals, like CH3 electrophile? Their are differing and opposite answers to all on internet, some saying "Free radical is neither a nucleophile nor an electrophile because it does not seek out positively or negatively charged reactants", others say "Since methyl radical contains 7 electron ( 4 from C and 3 from H) and needs 1 more electron to complete its octet, so it will accept electron from some species and will behave as Lewis acid." and others say "I don’t think that methyl free radical is a Lewis acid. According to the definition of Lewis acid, Lewis acids accept a pair of electrons". Exclusive Editor  Notify Me! 17:19, 31 January 2024 (UTC)
 * Methyl radical can indeed accept an electron and form unstable methyl anion, which (but not the radical!) is a Lewis base. Ruslik_ Zero 19:26, 31 January 2024 (UTC)