Aluminium and phosphorus are close to one another in the periodic table but the p3- ion is much larger than the al3+ ion. explain the reason for this change in size.

The P" ion has an electh arrangement of 2,8,8 ie three filled
electron energy level: The AP' ion has on electron
arrangement of 2,8 ie two filled electron energy levels. The
third electron energy level is further away from the nucleus
than the second and so the P" ion is the larger ion

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Radon-222 or rn-222 has a half-life of 3.82 days. to determine the fraction of an original sample of rn-222 that remains unchanged after 7.646 days, we calculate the amount of rn-222 remaining after 7.646 days and divide it with the original amount. using 1 gram as a basis and using half-life calculation methods, we can determine that  0.249 or 0.25  grams of rn-222 will remain, and thus the fraction remaining is 0.25 or 1/4.