Question

Name the first element and the last element of period two.

Answer 1

Step-1: Introduction

The arrangement of elements into groups and periods on similarity in chemical properties and in increasing atomic number is called modern periodic table.

The horizontal row that contains elements in ascending atomic number is called a period. There are seven periods in modern periodic table. The elements of a period have different atomic numbers and different valence electrons.

Step-2: Period 2 elements

The period 2 consists of eight elements. In this period, the K-shell of the atom of each element contains 2 electrons and the L-shell of each atom is being filled by electrons in the ascending order of atomic numbers. It is called a short period.

In period 2, the first element is Lithium ($\mathrm{Li}$), it contains 1 electron in its valence shell and it is an alkali metal.

In period 2, the last element is Neon ($\mathrm{Ne}$), it contains 8 electrons in its valence shell and it is a noble gas.

Therefore, the first element is Lithium and the last element is Neon of period 2.