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. Thus it is complicated to synthesize new elements. Scientists have hypothesized that there is an "island of stability," a group pf atoms with the right ratio of protons to neutrons that would allow them to exist for longer periods of time and be studied. This idea, however, has not been proved. As of today, elements up to the atomic number 118 have been discovered. Several are waiting for IUPAC's confirmation and formal naming. 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. Thus it is complicated to synthesize new elements. Scientists have hypothesized that there is an "island of stability," a group pf atoms with the right ratio of protons to neutrons that would allow them to exist for longer periods of time and be studied. This idea, however, has not been proved. As of today, elements up to the atomic number 118 have been discovered. Several are waiting for IUPAC's confirmation and formal naming. Therefore, the next element left to be discovered would have an atomic number of 119.
