Hi scientists of lemmy, I’m a computer scientist with basic college level physics and an interest in physics.

I was reading Cosmos by Carl Sagan yesterday and he mentions that if you use a Geiger counter next to an uranium ingot you will detect the uranium’s spontaneous decay as a stream of helium nucleei.

Does helium nucleei mean 2 protons and some number of neutrons? What happened to the respective electrons? Does this mean that each uranium atom, with 92 protons, entirely splits into 46 helium nucleei or does it release some number of helium nucleei leaving another element behind? How does the concept of half life play into this? Does it mean that in a uranium half life, half of my ingot would’ve become helium? Finally, how is this stream of helium nucleei so dangerous to living beings?

Thanks for your attention