Periodicity is best defined as:
the fact that elements increase in atomic mass in a regular way
the repeating nature of physical and chemical properties with atomic numbe
the regular growth of atomic size with atomic mass
the consistent decrease of nuclear charge with atomic mass
the repeating nature of atomic nuclear structure

The repeating nature of physical and chemical properties with atomic number

Explanation:

Periodic table is designed in a way in which elements are divided in groups and periods. Periods are rows and groups are columns. The elements in groups share similar properties due to the same number of valence electrons they have. Going along each period, we'll always get back to the same group at some point. This is why we have periodic trends, the trends repeat gradually when we finally reach the same group we're analyzing.

Physical and chemical properties vary periodically. For example:

answer; ///i do believe that the correct answer is (b); ///particle composed of two or more atoms bonded together;

the grams   of   barium that   are in   2.3 x 10^23   atoms of barium   is   52.4 g (answer c)

    calculation

mass = moles   of ba   x molar   mass of ba

  molar mass of ba from periodic table=   137.3 g/mol

  use the   avogadro's law   constant   to   calculate the moles of barium

  that   is     1 mole =   6.02   x 10^23 atoms

                    ? moles = 2.3 x 10^23   atoms

by cross   multiplication

=(1 mole   x 2.3x 10^23 atoms)   / 6.02   x10^23 atoms)=   0.382   moles

mass   is therefore = 137.3   g/mol x 0.382 mol = 52.4 ( answer c)

explanation: