Which of the following statements is correct about the periodic table?

To solve this question, let’s break down the fundamental organization of the Periodic Table.

1. Analyze the Question

The question asks us to identify the correct statement regarding the trends and properties of elements as they are arranged in the Periodic Table.

2. Explain the Concepts

• Periods: These are the horizontal rows. Elements in the same period have the same number of electron shells. As you move from left to right across a period, the atomic number increases by one, meaning one proton and one electron are added to the atom. This results in the number of valence electrons increasing by one for each subsequent element.
• Groups: These are the vertical columns. Elements in the same group have the same number of valence electrons, which is why they share similar chemical properties.
• Metallic/Non-metallic Trends: As you move across a period from left to right, the metallic character decreases and the non-metallic character increases because the atoms become smaller and hold onto their electrons more tightly (higher electronegativity).

3. Evaluate the Options

• Option A: Incorrect. Elements in the same group have the same number of valence electrons, not the same period.
• Option B: Correct. As you move across a period (e.g., from Lithium to Neon), each element adds one electron to the valence shell. Therefore, the number of valence electrons increases progressively.
• Option C: Incorrect. Elements in the same period have the same number of electron shells, not the same group.
• Option D: Incorrect. Non-metallic properties actually increase across a period from left to right, they do not decrease.

4. Conclusion

Based on the periodic trends, the number of valence electrons increases by one as you move from one element to the next across a period. This confirms that Option B is the accurate statement.

Exam Tip

Remember the "Group vs. Period" rule:

• Group = Grouping of valence electrons (same number).
• Period = Physical shells (same number of shells). If you get confused, just look at the first two elements of Period 2: Lithium (Group 1, 1 valence electron) and Beryllium (Group 2, 2 valence electrons). This proves the number increases across the period!