Explanation

1. 4f is closer to nucleous and not 6s.

2. But still 6s fills first because aufbau rule states that electrons fill first in orbitals with lower energy (i.e. lower value of sum of principal quantum number and azimuthal quantum number).

3. Don't confuse with energy, the one with lower principal quantum number will be inner.

Given:

Ratio of diameter of $$2$$ nuclei = $$1:2$$

To find the Ratio of their mass number.

As we know the - Radius of the nucleus is given as:

$$R=r_0A^{1/3}$$

$$A= Mass\ number$$, $$R=Radius\ of\ the\ nucleus$$, $$r_0=Nucleon\ number=1.25\ fm$$

As, $$\frac{D_1}{D_2}=\frac{1}{2}$$

Radius is just half of diameter as $$Radius\ \times \ 2=Diameter$$

So ratio of Radius$$=\frac{1}{2}$$

$$\frac{R_1}{R_2}=\frac{r_0\ A_1^{1/3}}{r_0\ A_2^{1/3}}$$

So, $$R^3\propto \ A$$

So Ratio of mass number i.e. $$\frac{A_1}{A_2}=\frac{1}{8}$$

optiin C is correct.

$$\alpha$$ -particles are essentially helium ions, and these are Massive and are Poorly penetrating.

$$\beta$$ -radiation are fast-moving electrons, and these are slightly more penetrating with respect to $$α$$-particles

$$\gamma$$ -radiation are faster moving particles, on the photonic scale. And these have the most penetrating power. They require lead shielding of several mm for safe containment.

Hence answer is Option A

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