Question

Find the Mendeleev’s periodic table group number of the following elements from their hydrides and oxides formula.

Elements	Oxide formula	Hydride formula	Group number
A	${A_2}{O_3}$	$A{H_3}$
B	${A_2}{O_7}$	$AH$
C	${A_2}{O_5}$	$A{H_3}$

Answer 1

As we know that in the world there are a lot of elements in various forms. For study and developing purposes, classification happens. Periodic table used to study the elements in easy form. If one new element is discovered, it means, based on the physical and chemical properties we placed in the periodic table.
In general, modern periodic table ordering is based on the atomic number of the atoms. The lowest atomic number starting from the first and followed by a higher atomic number.
Depending on the energy level of the outermost shell in the atoms, periods are classified and place the atom in respective periods. Depending on the electrons shielding and size and physical behaviour of the atom, groups are coming.

Complete answer:
The Mendeleev’s periodic table group number of the following elements from their hydrides and oxides formula is given below,

Elements	Oxide formula	Hydride formula	Group number
A	${A_2}{O_3}$	$A{H_3}$	$3$
B	${A_2}{O_7}$	$AH$	$7$
C	${A_2}{O_5}$	$A{H_3}$	$5$

Note:
We need to remember that in a generally modern periodic table, metallic atoms are placed on the left side of the table and non-metallic atoms are placed on the right side of the table. Metalloids and transition elements are placed in between metal and non-metal elements. Below the two rows are there. There are nothing but lanthanides and actinides. These are f-block elements. The atomic number of the element is nothing but the number of electrons or number of protons. The mass number of the atom is nothing but the sum of the number of protons and the number of neutrons. In general we move left to right metallic properties of the atom decreases. We move right to left and non-metallic property decreases.