Answer:
From the arrangement of electrons
Explanation:
The atomic numbers of the elements in the various groups differ because they contain different numbers of protons.
Atomic number of an element is the number of protons in that element and it is a property that is used to distinguish one element from another.
Elements are substances that contains atoms which cannot be broken down further into any smaller substances.
Periodic table is a structured table that arranged these elements according to the number of atoms they contain in their shells.
In a periodic table, these elements appear in periods and in groups.
The groups contain elements that share the same number of atoms in their outermost shell.
Therefore, group 1, 2, 13 and 18 contain elements that vary because they contain different numbers of protons.
Learn more here:
https://brainly.com/question/24674837
