Nitrogen (atomic number $=7$) and phosphorus (atomic number $=15$) belong to group $15$ of the periodic table. Write the electronic configuration of these two elements. Which will be more electronegative and why?

Identify the elements.

Two shells with atomic number less than two than that of Nitrogen.

Identify the elements.

Three shells which are completely filled.

Identify the elements.

Atomic number$-1$

Identify the elements:

Group $15$ and period $4$

Identify the elements.

Liquid with atomic number one less than that of TI.

Consider the following statements.

I. Dobereiner's triads had a great significance in predicting atomic mass and properties of middle element.

II. Law of octaves is based upon octaves found in music.

III. Eka-boron and eka-aluminium were named as scandium and gallium, later on.

Identify the correct statements.