The statement that is incorrect for the periodic classification of elements is:

1. The properties of elements are a periodic function of their atomic number.

2. Non-metallic elements are lesser in number than metallic elements.

3. The first ionization energies of elements along a period do not vary in a regular manner with an increase in atomic number.

4. For transition elements, the d-subshells are filled with electrons monotonically with an increase in atomic number.

The ions O^2-, F^-, Na⁺, Mg^2+, and Al³⁺ are isoelectronic. Their ionic radii show [2003]

1. an increase from O^2- to F^- and then decrease from Na⁺ to Al³⁺

2. a decrease from O^2- to F^- and then increase from Na⁺ to Al³⁺

3. a significant increase from O^2- to Al³⁺

4. a significant decrease from O^2- to Al³⁺

An example of metalloid elements in the periodic table is:

The element with atomic number 26 is:

1. A non-metal

2. Krypton

3. Iron

4. Manganese

The alkali metals have:

1. highest ionization energy

2. largest atomic radii

3. highest density

4. highest electronegativity

The telluric helix was given by:

1. Newland

2. Mendeleev

3. Lothar Meyer

4. De-chancourtois

The element with atomic number 30 is expected to be present in:

1. IB group

2. IA group

3. IIA group

4. IIB group 

The correct order of acid strength is:

1. ${\mathrm{Cl}}_2{\mathrm{O}}_7>{\mathrm{SO}}_2>{\mathrm{P}}_4{\mathrm{O}}_{10}$

2. ${\mathrm{CO}}_2>{\mathrm{N}}_2{\mathrm{O}}_5>{\mathrm{SO}}_3$

3. ${\mathrm{Na}}_2\mathrm{O}>\mathrm{MgO}>{\mathrm{Al}}_2{\mathrm{O}}_3$

4. ${\mathrm{K}}_2\mathrm{O}>\mathrm{CaO}>\mathrm{MgO}$

Which among the following elements is the bridge element?

1. K

2. O

3. Mg

4. Pb

Four successive members of the first-row transition elements are listed below with their atomic numbers. Which one of them is expected to have the highest third ionisation enthalpy?

1. Vanadium (Z = 23)

2. Chromium (Z = 24)

3. Iron (Z = 26)

4. Manganese (Z = 25)