Pb2+ is 119pm wide while Ca2+ is 100pm, so still a small enough difference in ionic radii for lead (II) ions to compete for uptake in bone mineralization.

I’m on mobile & couldn’t find a full text link to this paper but they mention risks of Pb intoxication during bone turn over processes here in the last sentence of the abstract: https://www.sciencedirect.com/science/article/abs/pii/S0300483X16303031

My pet theory on the Boomers’ behavior is that lead ions are the same atomic radius and charge as calcium ions, so the lead they were taking up as children has been sequestered in bones until the past decade or so when those’ve begun to demineralize, leaching the previously-sequestered lead back into the bloodstream to the brain

Yep, carbon makes 4 bonds but C-H ones are implied. Idk how well I can convey this with ASCII characters but a ”/\" would be H3C—CH2—CH3 (propane) molecule since there are 3 points on the triangle denoting the carbon atoms, the 2 lines connecting the points are the 2 C—C bonds, and you fill in the remaining bonds on each carbon atom up to the 4 total bonds. Similarly a "\/\/\” would be n-hexane (n just meaning a normal linear chain instead of cyclohexane, a ring) which can be depicted as H3C—CH2—CH2—CH2—CH2—CH3