A neutral atom of beryllium-9 (${}_4^{9}Be$) consists of a nucleus containing protons and neutrons, with electrons in outer orbits. Identify the names of: (i) the negative subatomic particles in the outer orbits, and (ii) the uncharged subatomic particles in the nucleus.

An atom of sodium has the nuclide notation:

State the number of protons, neutrons, and electrons in this neutral atom.

A radioactive isotope of sodium (${}_{11}^{24}Na$) has a half-life of 15 hours. A sample contains 320 mg of this isotope. Calculate the time taken for this isotope to decay to 10 mg.