Final answer:
The fourth element in groups 1 and 2 is 16 greater in atomic number than the first element, and in group 18, it is 18 greater. This is calculated by finding the atomic numbers on the periodic table and comparing the first and fourth element's numbers.
Step-by-step explanation:
The question pertains to the difference in atomic numbers of elements in groups 1, 2, and 18 of the periodic table at their fourth respective positions. By looking at the periodic table, one can find the atomic numbers of these elements. The fourth element in group 1 is potassium (K) with atomic number 19; in group 2, it is calcium (Ca) with atomic number 20; and in group 18, it is krypton (Kr) with atomic number 36. To find out how much greater the atomic number of the fourth element is compared to the preceding elements in each group:
- Group 1: Lithium (Li), atomic number 3 -> Potassium (K) 19 - 3 = 16
- Group 2: Beryllium (Be), atomic number 4 -> Calcium (Ca) 20 - 4 = 16
- Group 18: Argon (Ar), atomic number 18 -> Krypton (Kr) 36 - 18 = 18
Thus, for group 1 and group 2, the atomic number of the fourth element is 16 greater than that of the first element, while for group 18 it is 18 greater.