118 elements.
In a periodic table, elements are arranged in increasing order of atomic number. There are 18 groups and 7 periods in the periodic table. On moving left to right in a period, group number increases and on moving top to bottom in a group, period increases. There are approximately 118 elements in the periodic table. The first element is hydrogen (H) with atomic number 1 and 118th element is oganesson (Og) with atomic number 118.