Question

Are elements with similar chemical properties more likely to be found in the same period or in the same group?

Answer 1

Similar chemical properties are a consequence of the same number of valence electrons or the same type of outer electronic configuration that allows the elements to show similar kinds of reaction under particular set of conditions.

Complete Step By Step Answer:
The horizontal rows in the modern periodic table are called rows and the vertical columns are called groups. The rows consist of atoms in which the electrons are being added into the same shell and the atomic numbers keep increasing by one as we move from the left side of a period to its right side.
The columns consist of atoms that have been clubbed together due to a periodic repetition of their physical and chemical properties. The elements belonging to a particular group have the same number of valence electrons and a general outer electronic configuration in which only the shell number increases as we descend a group.
Similarity in chemical properties can be observed when electrons have similar electropositive or electronegative characters, same number of valence electrons and a similar configuration that allows them to give specific products with a given set of reactants.
Thus, the elements with similar chemical properties form a group and are not part of a period.

Note:
Even though the properties of elements belonging to the same group are similar in nature, yet the changes in size, ionization energy, nuclear charge and other important attributes continue to take place when going down a group.