Question

Table given below shows a part of the periodic table:

H							He
Li	Be	B	C	N	O	F	Ne
Na	Mg	Al	Si	P	S	Cl	Ar

Using this table explains why?
1. Li and Na are considered as active metals.
2. Atomic size of Mg is less than that of Al
3. Fluorine is more reactive than chlorine.

Answer 1

Periodic table is the arrangement of elements in order of their increasing atomic number. It was given by the scientist named Mendeleev and this table consists of 7 groups and 18 periods rather than this it also contains two lines of elements below the table known by the name lanthanide and actinide.

Complete step by step answer:
1. Li and Na are considered as active metals: Active metals are those metals which have only one electron in their valence shell and they readily lose their single electron and attain their stable configuration of nearest noble gases. Li and Na both are active metals as they also have one electron in their valence shell $Li-1{{s}^{2}}2{{s}^{1}}$and $Na-1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{1}}$and lose one electron to form stable gas configuration.
2. Atomic size of Mg is less than that of Al: Mg is placed after Na in the same period and we know that atomic size goes on decreasing while moving left to right across a period due to increase in nuclear charge which results in a stronger pull of the outer electrons towards the nucleus.
3. Fluorine is more reactive than chlorine: Fluorine and chlorine both belong to group 17 but fluorine is more electronegative than chlorine therefore it is considered to be more reactive.

Note: Electronegativity term refers to the tendency of an atom in a molecule which attracts a shared pair of electrons towards itself. It is a dimensionless property and effective nuclear charge can be defined as the positive charge experienced by an electron.