In a given column of the periodic table the elements have . a. similar properties
b. sequential atomic numbers
c. similar atomic masses
d. the same densities

a. similar properties

Explanation:

In a given column of the periodic table, the elements have similar properties.

A column on the periodic table is known as a group or family. The group is a vertical arrangement of elements  on the periodic table.

Elements in the same group have the same number of valence electrons after their group number.

For example, all the elements in group 1 have one valence electron. Those in group 2 have 2 valence electrons.

The valence electrons of an atom determines its chemical properties. So, all elements in the same group have the same chemical properties.

explanation:

metals have excess of electrons whereas non-metals have deficiency of electrons. thus, in order to gain stability metals easily donate their electrons to the non-metals.

for example, electronic configuration of sodium is and electronic configuration of phosphorous is .

when a phosphorous atom and sodium atom combine together then sodium will donate is extra one electron to the phosphorous atom. as a result there will be formation of ionic bond between sodium and phosphorous.

the reaction will be as follows.

there, are three sodium sodium atoms and each of them will donate its one extra electron to phosphorous atom. thus, the sub-shell of phosphorous gets completely filled.  

thus, we can conclude that electrons are transferred from atoms of sodium to atoms of phosphorous. this transfer makes the sodium atoms donate one electron and the phosphorous atoms to gain one electron. as a result, the sodium and phosphorus atoms strongly attract each other.