The element having atomic number 19, is:

1. an inert gas

2. a metal with oxidation number +1

3. a non-metal with oxidation number -3

4. a metal with oxidation number -3

Which of the following has the least density?

1. Na

2. Li

3. Mg

4. K

Eka aluminium and Eka silicon are now known as:

An element having the electronic configuration of its atom ns² np² should have similar properties to those of:

1. Sodium

2. Carbon

3. Magnesium

4. Oxygen

The order of basic character of given oxides is:

1. Na₂O > MgO > Al₂O₃ > CuO

2. MgO > Al₂O₃ > CuO > Na₂O

3. Al₂O₃ > MgO > CuO > Na₂O

4. CuO > Na₂O > MgO > Al₂O₃

Which of the following exhibits variable oxidation states?

The lightest metal in the periodic table is:

1. H

2. Mg

3. Ca

4. Li

The electronic configuration that represents the d-block element is: 

1. 1s² 2s² 2p⁶ 3s²3p⁶3d¹⁰ 4s²4p⁶

2. 1s² 2s² 2p⁶ 3s²3p⁶3d¹⁰ 4s²4p¹

3. 1s² 2s² 2p⁶ 3s²3p⁶3d¹⁰ 4s²

4. 1s² 2s² $2p^6$ 3s²3p⁶ 4s²

The most common oxidation state of cerium (Ce) is:

1. +5, +3

2. +5, +4

3. +3, +4

4. +3, +5

Which of the electronic configuration of an atom has the lowest ionization enthalpy? 

1. 1s²,2s²2p⁵

2. 1s²,2s²2p³

3. 1s²,2s²2$p^6$,3s¹

4. 1s²,2s²2p⁶