The element that contains a complete d subshell in the ground state : <u>Cu</u>
<h3>Further explanation
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In an atom, there are energy levels in the shell and sub shell.
This energy level is expressed in terms of electron configurations.
Writing the electron configuration starts from the lowest to the highest subshell's energy level (following Aufbau rules)
Electron filling in subshells using the following sequence
1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5p⁶, 6s², etc.
And the element whose electron configuration occupies the sub shell d lies in the transition group or group B in the periodic system
Electrons can move the shell up or down by releasing energy or absorbing energy
So it can be concluded that there are 2 conditions:
Ground state is the state of electrons filling shell with the lowest energy levels.
Excited state is the state of electrons which occupies a higher energy level
In filling electrons in subshell d there are half-full and full rules because of the tendency of electrons to get stability (not following the Aufbau rule)
Example
Cr atomic number 24: [Ar] 4s² 3d⁴ [Ar] 4s¹ 3d⁵
Cu atomic number 29: [Ar] 4s² 3d⁹ [Ar] 4s¹ 3d¹⁰
Mo atomic number 42: [Cr] 5s² 4d⁴ [Cr] 5s¹ 4d⁵
So the element of the lowest atomic number that contains a complete subshell in the ground state has an electron configuration
1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹, 3d¹⁰
which is owned by the element Cu
<h3>
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