Neco 2025 Chemistry Question 2

Practice essay / theory question 2 from the 2025 Neco Chemistry examination. This question covers Periodic Table .

Neco 2025 Chemistry Essay / Theory

Topic: Periodic Table

Question 2 NECO • 2025 • CHEMISTRY • essay

The illustration presents a section of the periodic table covering period 3 (elements Na to Ar). The atomic radii (in picometres) of the first and last elements in the period are given: Na = 186 pm, Ar = 71 pm.

Question Parts

( a )

State the group number and the family name of chlorine (Cl) as shown in the diagram.

( b )

Using the diagram, determine the number of valence electrons of sulphur (S).

( c )

Assuming a linear decrease in atomic radius across period 3, estimate the atomic radius of phosphorus (P, atomic number 15). Show your working and give the answer to the nearest picometre.

( d )

Briefly explain the observed trend in atomic radii across period 3, referencing effective nuclear charge.

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About This Question

This is Neco 2025 Chemistry Question 2. It is one of the essay questions from the 2025 Neco Chemistry examination.

The question covers Periodic Table .

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