41) Which of the following electron configurations is incorrect as written?
A) 1s22s22p63s23p64s23d104p4
B) 1s22s22px22py22pz23s2
C) 1s22s22p63s23p63d10
D) 1s22s22p63s2
42) The electron configuration shown below is for the element __.
1s22s22p63s23p64s23d104p4
A) Se
B) Ga
C) As
D) Br
43) Which element has the electron configuration [Kr]5s24d105p2?
A) Sn
B) Sb
C) Pb
D) Ge
44) Hund’s rule is needed in drawing an orbital diagram for which of the following elements?
A) krypton
B) lithium
C) boron
D) selenium
45) The number of unpaired electrons present in a magnesium atom is __.
A) 0
B) 1
C) 3
D) 2
46) How many unpaired electrons are in a Ru atom?
A) 2
B) 4
C) 6
D) 0
47) In which pair are the atoms, Ba and Xe, correctly identified regarding their magnetic properties?
A) Ba: diamagneticXe: diamagnetic
B) Ba: diamagneticXe: paramagnetic
C) Ba: paramagneticXe: diamagnetic
D) Ba: paramagneticXe: paramagnetic
48) Which of the following atoms is paramagnetic?
A) Ar
B) Ca
C) O
D) Zn
49) In the electron configuration of an arsenic atom, there are __ unpaired electrons.
A) 2
B) 0
C) 1
D) 3
50) How many unpaired electrons are there in a phosphorous atom?
A) 1
B) 2
C) 3
D) 4
The Correct Answer and Explanation is :
41) Which of the following electron configurations is incorrect as written?
The correct answer is B) 1s²2s²2px²2py²2pz²3s².
Explanation:
- Option A (1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴) is correct. This corresponds to the element Selenium (Se), which follows the Aufbau principle, Pauli exclusion principle, and Hund’s rule.
- Option B is incorrect. The 2p subshell can hold a maximum of 6 electrons, not 4, and therefore the electron configuration “2px²2py²2pz²” is incorrect because it exceeds the capacity of the 2p orbital. The correct configuration for the 2p orbital would be 2px²2py²2pz², which would fill all 6 available 2p electrons.
- Option C (1s²2s²2p⁶3s²3p⁶3d¹⁰) is correct, as it represents the element Zinc (Zn) where the 3d subshell is completely filled.
- Option D (1s²2s²2p⁶3s²) is correct for Magnesium (Mg), which only has electrons up to the 3s orbital.
42) The electron configuration shown below is for the element ________. 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴
The correct answer is A) Se (Selenium).
Explanation: The electron configuration 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴ represents Selenium (Se), an element in the fourth period and group 16 of the periodic table. The configuration corresponds to 34 electrons, matching the atomic number of Selenium.
43) Which element has the electron configuration [Kr]5s²4d¹⁰5p²?
The correct answer is A) Sn (Tin).
Explanation: The electron configuration [Kr]5s²4d¹⁰5p² corresponds to Tin (Sn), which has an atomic number of 50. The configuration shows the 5s, 4d, and 5p subshells, indicating the element is in period 5, group 14 of the periodic table.
44) Hund’s rule is needed in drawing an orbital diagram for which of the following elements?
The correct answer is C) Boron.
Explanation: Hund’s rule states that electrons will fill degenerate orbitals (orbitals of the same energy) singly before pairing. For Boron, with an electron configuration of 1s²2s²2p¹, the electrons in the 2p orbital will occupy individual orbitals before pairing, and this rule would apply in drawing its orbital diagram.
45) The number of unpaired electrons present in a magnesium atom is ________.
The correct answer is A) 0.
Explanation: Magnesium (Mg) has the electron configuration 1s²2s²2p⁶3s². The 3s orbital is completely filled with 2 electrons, and since it has no unpaired electrons, the answer is 0.
46) How many unpaired electrons are in a Ru atom?
The correct answer is B) 4.
Explanation: Ruthenium (Ru) has an atomic number of 44, and its electron configuration is [Kr]5s²4d⁶. In the 4d subshell, there are 6 electrons, and based on Hund’s rule, 4 of these electrons will be unpaired, giving a total of 4 unpaired electrons.
47) In which pair are the atoms, Ba and Xe, correctly identified regarding their magnetic properties?
The correct answer is C) Ba: paramagnetic Xe: diamagnetic.
Explanation:
- Ba (Barium) has the electron configuration [Xe]6s², and since it has unpaired electrons, it is paramagnetic.
- Xe (Xenon) has the electron configuration [Kr]4d¹⁰5s²5p⁶, which is completely filled and has no unpaired electrons, making it diamagnetic.
48) Which of the following atoms is paramagnetic?
The correct answer is C) O (Oxygen).
Explanation: Oxygen has the electron configuration 1s²2s²2p⁴, and the 2p subshell has 2 unpaired electrons, making it paramagnetic (attracted to magnetic fields).
49) In the electron configuration of an arsenic atom, there are ________ unpaired electrons.
The correct answer is D) 3.
Explanation: Arsenic (As) has the electron configuration [Ar]4s²3d¹⁰4p³. In the 4p subshell, there are 3 unpaired electrons.
50) How many unpaired electrons are there in a phosphorus atom?
The correct answer is C) 3.
Explanation: Phosphorus (P) has the electron configuration 1s²2s²2p⁶3s²3p³. In the 3p subshell, there are 3 unpaired electrons.