The element in the missing box is___ . (Use the symbol from the periodic table, not the whole name.)
238/92u>4/2he+234/90____
th
The element in the missing box is Th (Thorium).
To determine the element in the missing box, we need to understand the given nuclear reaction and use the information from the periodic table.
In the given reaction, the isotope with mass number 238 and atomic number 92 (Uranium) undergoes radioactive decay. It releases an alpha particle, which has a mass number of 4 and an atomic number of 2 (Helium). After the decay, a new isotope is formed with a mass number of 234 and an atomic number of 90.
To identify the missing element, we can look for an element on the periodic table with an atomic number of 90. Consulting the periodic table, we find that the element with atomic number 90 is Thorium (Th). Therefore, the missing element in the reaction is Thorium (Th).
So, the answer is Th.