<span>the reaction is endothermic
</span><span>the δh is positive</span>
That's kind of a ponderous way to describe it, but your 'X' represents
the absolute temperature of the ideal gas.
After a radioactive atom decays, it is the same element that it
was before with no measurable change in mass. the decay that is present is
gamma decay because gamma decay has photons which has no mass unlike alpha and
beta decay.
<span>6s²4f¹⁴5d¹⁰6p²
6 shows that the element is in the 6 period,
6p² shows that the element is in the 14th group. (1 and 2 groups have s -electrons as last ones, 13 group has s²p¹, and 14 group has s²p²)
The element is Pb.
</span>
