Question

If an element with Z = 120 is discovered, then which group of elements will it belong to?

• A. Alkaline earth metals
• B. Alkali metals
• C. Halogens
• D. Noble gases

Hint:

Remember the atomic numbers of the noble gases: He (2), Ne (10), Ar (18), Kr (36), Xe (54), Rn (86), and Og (118).
Any element with \(Z = \text{noble gas atomic number} + 1\) is an alkali metal (Group 1).
Any element with \(Z = \text{noble gas atomic number} + 2\) is an alkaline earth metal (Group 2).

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks us to identify the group in the periodic table to which a newly discovered element with atomic number \(Z = 120\) would belong.

Step 2: Key Formula or Approach:
To find the position of any element in the periodic table:
1. We locate the nearest noble gas that precedes or ends the period.
2. Period 7 of the modern periodic table is completed at the noble gas Oganesson (\(\text{Og}\)) with atomic number \(Z = 118\), which belongs to Group 18.
3. Elements with atomic numbers greater than 118 will enter the newly started Period 8.

Step 3: Detailed Explanation:
Let's trace the atomic numbers sequentially starting from the end of Period 7:
- \(Z = 118\) is Oganesson (\(\text{Og}\)), which is the noble gas ending Period 7 in Group 18.
- \(Z = 119\) will be the first element of Period 8. It will be placed in Group 1 (Alkali metals) with an outer electronic configuration of \([118\text{Og}] 8s^1\).
- \(Z = 120\) will be the second element of Period 8. It will be placed in Group 2 (Alkaline earth metals) with an outer electronic configuration of \([118\text{Og}] 8s^2\).
- Therefore, the element with \(Z = 120\) belongs to the alkaline earth metals group.

Step 4: Final Answer:
The element with \(Z = 120\) will belong to the alkaline earth metals group, which corresponds to option (A).