Questions in nuclei

Select	Question
	A radioactive nucleus with Z protons and N neutrons emits an $\alpha$ -particle, 2 $\beta$ -particles and 2 gamma rays. The number of protons and neutrons in the nucleus left after the decay respectively, are
	99% of a radioactive element will decay between
	1 mg gold undergoes decay with 2.7 days half-life period, amount left after 8.1 days is
	Certain radio-active substance reduces to 25% of its value in 16 days. Its half-life is
	In the disintegration series $^{238}_{92} U \xrightarrow{\alpha}X \xrightarrow{\beta}^A_ZY$ The value of Z and A respectively will be
	The decay constant of a radioactive element is $1.5 \times {10^{ - 9}}$ per second. Its mean life in seconds will be
	The half-life of a radioactive substance against $\alpha$ -decay is $1.2 \times {10^7}s$. What is the decay rate for $4 \times {10^{15}}$ atoms of the substance
	10 gm of radioactive material of half-life 15 year is kept in store for 20 years. The disintegrated material is
	In a sample of radioactive material, what percentage of the initial number of active nuclei will decay during one mean life
	The S.I. unit of radioactivity is