Question

What do groups and periods represent on the periodic table

Answer 1

Answer:

: The vertical column of the periodic table signifies the number of valence electrons in an element. Periods: The horizontal rows in the periodic table signify the number of electron shells in an element. Families: Elements that have the same number of valence electrons and therefore similar properties.

Explanation:

(a). The horizontal rows of elements in a periodic table are called periods. Characteristics:

(i) The elements in a period have consecutive atomic numbers.

(ii) The number of elements in period is fixed by the maximum number of electrons which can be accommodated in various shells.

Characteristics:

The vertical columns in a periodic table are called group characteristics

(i) The elements in a group do not have consecutive atomic numbers.

(ii) All the elements in a group have similar electronic configurations and show similar properties.

(b). The size of the atom decreases on moving from left to right in a period. As we move from left to right in a period the atomic number of elements increases which means that the number of protons and electrons in the atom increases. The electronic configuration of the atoms increases in the same shell. Due to the large positive charge on the nucleus, the electrons are pulled in close to the nucleus, and the size of the atom decreases. Ongoing down in a group of the periodic table the atomic size increases due to the increases in atomic shells.

(c).

(i) The atomic size increases gradually from lithium to francium due to the addition of a shell.

(ii) The metallic character increases from lithium to francium.  

(d). On going down in a group of the periodic table, the atomic size and metallic character increase. When we move down from top to bottom in group 1 of alkali metals, the size of atoms increases gradually from lithium to francium. In group 1 of alkali metals lithium is the least metallic element whereas francium is the most metallic element.

(e). Periods have elements with consecutive atomic numbers.