Question

The nucleus of a radium-226 atom is unstable, which causes the nucleus to spontaneously

Answer 1

The answer is (3) decay. An atom whose nucleus is unstable is said to be "radioactive," and its nucleus undergoes nuclear decay.

Answer 2

Answer: The nucleus of radium-226 is unstable and hence undergoes decay.

Explanation: Radium has many isotopes. One of them is $_{88}^{226}\textrm{Ra}$ which has 88 protons and 138 neutrons. It is a radioactive isotope and undergoes decay process.

This isotope undergoes alpha - decay and produces Radon-222 isotope.

Equation for alpha - decay follows:

$_{88}^{226}\textrm{Ra}\rightarrow _{86}^{222}\textrm{Rn}+_2^4\alpha$

Hence, the nucleus of radium-226 undergoes decay process.