A student argued that the 3d orbitals will be filled only after the 4s orbital is completely filled in accordance with aufbau principle. Then another student opposed by saying that it is not true for certain elements like Cr and Cu.
Whose argument is correct?

A student argued that the 3d orbitals will be filled only after the 4s orbital is completely filled in accordance with aufbau principle. Then another student opposed by saying that it is not true for certain elements like Cr and Cu. Write electronic configuration of underset(24)(Cr) and underset(29)(Cu) . Justify your answer.

Silver atom has completely filled d- orbitals (4d") in its ground state. How can you say that it is a transition element?

Silver atom has completely-filled d-orbital (4d^105 s^1) in its ground state. How can you say- it is a transition element?

Write the correct order of filling elements in the subshell. 4s 3d 2p 3s 2s 1s 3p 4p

Arrange the following orbitals in the order in which electrons may be normally expected to fill them 3 s, 2 p, 3 p, 2 s, 3 d, 4 s

Make correct statements by filling in the symbols 'subset' or 'not a subset' in the blank spaces: i) '{2,3,4} ....{1,2,3,4,5}' ii) '{a, b, c} ....., {b,c, d}' iii) '{x: x' is a student of Class XI of, your school} ' . .{x: x' is a student of your school}' iv) '{x: x' is a circle in the plane} ' ....{x: x' is a circle in the same plane with radius 1 unit}' v) '{x: x' is a triangle in a plane} ' ....{x: x' is a rectangle in the plane}' vi) '{x: x' is an equilateral triangle in a plane} '......{x: x' is a triangle in the same plane)

Assertion : The outer electronic configurations of Cr and Cu are 3d^(5)4s^(1) and 3d^(10)4s^(1) respectively. Reason : Electrons are filled in orbitals in order of their increasing energies given by (n+l) rule.

Account for the following: a. The expected electronic configuration of copper is '[Ar] 3d^9 4s^2' but actually it is '[Ar] 3 d^(10) 4 s^1' b. In building up of atoms, the filling of 4s orbitals occurs before '3 d' - orbitals.

When the teacher asked to write the electronic configuration and box diagram of two elements with atomic number 24 and 29 respectively a student wrote the answer as follows. Z = 24, 1s^2 2s^2 2p^6 3s^2 Sp^6 3d^6 Z = 29, 1s^2 2s^2 2p^6 3s^2 Sp^6 3d^6 4s^2 If there is any mistake in the answer, correct it.