Question

What is the noble gas notation for the electron Br?

Answer 1

"Noble gas notation" means that in writing out an electron configuration for an atom, rather than writing out the occupation of each and every orbital specifically, you instead lump all of the core electrons together and designate it with the symbol of the corresponding noble gas on the periodic table (in brackets).

For example, if I wrote out the full electron configuration for a sodium atom, it would be `1s^2 2s^2 2p^6 3s^1`. But if I instead use noble gas notation, everything in the 1st and 2nd shells (the core electrons) would be designated as being equivalent to Neon, the closest noble gas that occurs before sodium on the periodic table. so using noble gas notation, the electron configuration of sodium becomes `[Ne]3s^1`.

An bromide ion should be only [Kr] since it has the same number of electrons as Krypton.