Question on: JAMB Chemistry - 2014
An element X has electron configuration 1s2 2s2 2p6 3s2 3p5. Which of the following statements is correct about the element?
A
lt has a completely filled p-orbital
B
lt has 5 electrons in its outermost shell.
C
lt belongs to group ll on the periodic table
D
lt is a halogen
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Correct Option: D
The electron configuration of element X is 1s2 2s2 2p6 3s2 3p5. Let's analyze the options:
- A. It has a completely filled p-orbital: The 2p orbital is completely filled (2p6), but the 3p orbital is not completely filled (3p5).
- B. It has 5 electrons in its outermost shell: The outermost shell is the 3rd shell, which has 2 electrons in the 3s orbital and 5 electrons in the 3p orbital. Thus, it has 2 + 5 = 7 electrons in its outermost shell. This statement is incorrect.
- C. It belongs to group II on the periodic table: The group number is determined by the number of valence electrons. Since there are 7 valence electrons, this is incorrect.
- D. It is a halogen: Halogens are in Group 17 (VIIA) and have 7 valence electrons, which is the case for element X. Therefore, this is the correct statement.
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