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Yes it can be confusing. Notice these groups are described as Main Groups, and also that the block in between (often called the d-block) is described as being for the Transition Metals. The "transition" metals were historically viewed as being in the transition from the simpler rules of chemical behaviour of the light elements of the 1st 3 rows to the more complex behaviour of the heavier ones from the 4th row onward. (As with so many things in science, history has a lot to do with how things end up being named.) Nowadays, it is really better to speak of the s-block, for the 1st 2 main groups, the p-block for groups 3-7 and 0, the d-block for the transition metals (and the f-block for the so-called lanthanides and actinides that are usually represented below the d-block.) But over the years there have been many different ways to display the table and also a variety of different numbering systems and naming conventions. So inevitably you will come across a few different ones in your reading. Just keep the shape in your mind: 2 columns of s-block metals on the left, 6 columns of p-block elements on the right, with the metal/non-metal diagonal running obliquely through them like a staircase, and the d- and f- block metals in the middle. The reason for the rather ungainly shape of the table is to do with the order in which electrons build up* in layers within the atom, as one moves through the table from lighter elements to heavier ones. Remember that It is the outer electrons (called the "valence" electrons) that are responsible for the chemical behaviour of the elements. The shape of the outermost layer, and how strongly or weakly bound the electrons in it are, is what determines how the element will behave in chemical reactions. * from the German Aufbauprinzip or building up principle, which explains how the behaviour of the outermost electrons is determined by quantum theory. You will get to that in due course. It's rather cool.

It’s not clear here if you think 10 AU is how far you need to disperse the material. The wikipedia article says “All scales larger than the Jeans length are unstable to gravitational collapse, whereas smaller scales are stable” which implies spreading the material far apart would be an unstable situation. What’s happening is that by spreading the material out the density drops, increasing the Jeans length, but the size of the cloud is smaller than 10AU, so the thermal energy exceeds the magnitude of the gravitational energy. The Jeans length is where they are equal. (It also seems that the analysis ignores the role of inelastic scattering in the process, which I’m sure astrophysicists have noticed, so it’s a more subtle situation, that is, the Jeans length would not be constant in time for a given mass and size)

Obviously not well enough known to be noted here. The issue is a practical one, that both GR and QM share since both assume infinite divisibility of space. The issue is that the smallest particles we have identified are about 15 orders of magnitude greater in size than the planck length and 20 orders of magnitude greater than we have successfully been able to probe. ( note I am measuring size by L units, not M units ie diameter not mass). If you want to probe the mathematics of the region between this sizes I recommend this book which take you from Brirkhoff and Von Neuman (1936) through Segal (1947) to Kakutani(1948) and Gleason (1953) and Bogachev (1998) for mathematical models of what happens with Borel sets in (possibly infinite Hilbert spaces (manifolds). The question of the meaning and existance of A*B and A + B and A-B and commutators is examined in great detail leading to Segals axiomatic statement of QM. It is how ever admitted that (axiom VII) the justification is 'that it works'. As my last reference indicated work has proceed since Mackay's 1963 original.

"Even people whose lives have been made various by learning sometimes find it hard to keep a fast hold on their habitual views of life, on their faith in the Invisible - nay, on the sense that their past joys and sorrows are a real experience, when they are suddenly transported to a new land, where the beings around them know nothing of their history, and share none of their ideas - where their mother earth shows another lap, and human life has other forms than those on which their souls have been nourished. Minds that have been unhinged from their old faith and love have perhaps sought this Lethean influence of exile in which the past becomes dreamy because its symbols have all vanished, and the present too is dreamy because it is linked with no memories.” ― George Eliot, Silas Marner

A similar strategy also explains the literal meaning of Brontosaurus: thunder lizard.