Assertion: Elements having atomic number 3 and 11 belong to the same group.

Reason: Elements having same number of valence electrons are placed in the same group.

Q. Assertion :Elements belonging to the same group have similar chemical properties. Reason: Elements of a group have same number of valence electrons.

Q.

Assertion: Elements with the same chemical properties are kept in the same group.

Reason: Elements in a group have the same number of electrons in the outermost shell hence they have similar chemical properties.

Q. When elements are placed in the order of their increasing atomic number,
the elements having the same number of __________ is repeated in such a way, so as to fall under the same group. Since, the electronic configuration of the valence shell electrons is same they show similar properties.

Q. Write scientific reason: Elements belonging to the same group have the same valency.

Q.

Fill in the blanks with correct option.

1. Properties of element are periodic function of their _______ (atomic mass/ atomic number/ relative atomic mass).

2. The elements having same _______(electronic configuration/ number of valence electrons) are placed in the same group.

3. In the modern periodic table the elements placed below sodium are expected to have________(lower/ higher) electronegativity than sodium and the elements placed above chlorine are expected to have ______(lower/ higher) ionization energy than chlorine.