Which of the following pairs shows opposite trends when moving from left to right in a period and from top to bottom in a group?

Which of the following statements is incorrect?

Which group is called the buffer group of the periodic table?

Consider the following statements:
$I.$ The radius of an anion is larger than that of the parent atom.
$II.$ The ionization energy generally increases with increasing atomic number in a period.
$III.$ The electronegativity of an element is the tendency of an isolated atom to attract an electron.
Which of the above statements is/are correct?

Which one of the following sets of ions represents a collection of isoelectronic species?

Represent different types of periodic properties in the periodic table.