Answer
Theoretically speaking, there is an infinite number of elements left to discover, because you can always continue adding one more proton to create another element. Practically, we have discovered that heavy elements tend to be very unstable because the ratio of protons to neutrons is unfavorable for stability. This is why the last elements discovered (103-118) are studied for so long to confirm discovery: they disintegrate in a matter of milli, micro or nano seconds. Therefore, the next element left to be discovered would have an atomic number of 119.
Work Step by Step
Theoretically speaking, there is an infinite number of elements left to discover, because you can always continue adding one more proton to create another element. Practically, we have discovered that heavy elements tend to be very unstable because the ratio of protons to neutrons is unfavorable for stability. This is why the last elements discovered (103-118) are studied for so long to confirm discovery: they disintegrate in a matter of milli, micro or nano seconds. Therefore, the next element left to be discovered would have an atomic number of 119.
