Asample of a radioactive nuclide has a mass of 10 g. how many half lives must transpire until less than 21% of the original sample is present?

3 half-lives.

Explanation:

Half-life time is constant for first-order reaction.

21% of the sample (10 g) represents (10.0 x 0.21 = 2.1 g).

10 g (first half-life) → 5 g (second half-life) → 2.5 g (third half-life) → 1.25 g.

∴ 3 half-lives are needed for the sample to reach less than 21% (<2.1 g) of its initial value.

because u need two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei to form isotopes.

so since they all have the same shape? i mean maybe because m& m and reeses are both chocolates