Multiple Choice
Which noble gas is used as the core in the electron configuration of antimony (Sb)?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following pairs of elements have the same ground-state electron configuration?
A
Cu and Ag
B
No two elements have the same ground-state electron configuration
C
O and S
D
Na and Mg
Verified step by step guidance1
Recall that the ground-state electron configuration of an element describes the arrangement of electrons in its atomic orbitals when the atom is in its lowest energy state.
Understand that elements in the same group (vertical column) of the periodic table often have similar valence electron configurations but differ in the total number of electrons and inner shell configurations.
For each pair, write out or consider their full ground-state electron configurations. For example, for Cu (Copper) and Ag (Silver), both are in group 11 but in different periods, so their configurations will be similar in valence but differ in inner shells.
Compare the electron configurations of each pair carefully to see if they are identical in all occupied orbitals, not just valence electrons. Remember that elements in different periods will have different principal quantum numbers for their orbitals.
Conclude that no two different elements have exactly the same full ground-state electron configuration because each element has a unique number of electrons filling orbitals in a specific order.
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