Electronic Structure MCQ's PDF

1. What shape is an "s" orbital? a) Double helix b) Dumbbell c) Spherical d) Hourglass Answer: c) Spherical *Explanation: The "s" orbital is spherical in shape.* 2. What is the shape of a "p" orbital? a) Spherical b) Hourglass c) Figure of 8 d) Cubic Answer: c) Figure of 8 *Explanation: The "p" o...

1. What shape is an "s" orbital? a) Double helix b) Dumbbell c) Spherical d) Hourglass Answer: c) Spherical *Explanation: The "s" orbital is spherical in shape.* 2. What is the shape of a "p" orbital? a) Spherical b) Hourglass c) Figure of 8 d) Cubic Answer: c) Figure of 8 *Explanation: The "p" orbital is shaped like a figure of 8.* 3. How many electrons can each orbital hold? a) 1 b) 2 c) 3 d) 4 Answer: b) 2 *Explanation: Each orbital can hold a maximum of 2 electrons which are paired with opposite spins.* 4. Which orbital group is filled first according to electron filling order? a) 3d b) 4s c) 4p d) 3s Answer: b) 4s *Explanation: The 4s orbital is filled before the 3d orbital.* 5. Which rule states that electrons fill orbitals singly first before pairing up? a) Pauli exclusion principle b) Heisenberg uncertainty principle c) Hund's rule d) Aufbau principle Answer: c) Hund's rule *Explanation: Hund's rule states that electrons occupy orbitals singly first before pairing up.* 6. What does the electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵ represent? a) Chromium (Cr) b) Copper (Cu) c) Iron (Fe) d) Cobalt (Co) Answer: a) Chromium (Cr) *Explanation: Chromium (Cr) has the exceptional configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵.* 7. What is the electronic configuration for an ion of Cl⁻ (chloride ion)? a) 1s² 2s² 2p⁶ 3s² 3p⁵ b) 1s² 2s² 2p⁶ 3s² 3p⁶ c) 1s² 2s² 2p⁶ 3s² 3p⁴ d) 1s² 2s² 2p⁶ 3s² 3p³ Answer: b) 1s² 2s² 2p⁶ 3s² 3p⁶ *Explanation: Chloride ion (Cl⁻) gains one electron resulting in the configuration 1s² 2s² 2p⁶ 3s² 3p⁶.* 8. Which of these blocks does the element with the configuration 4s² 3d⁴ belong to? a) s-block b) p-block c) d-block d) f-block Answer: c) d-block *Explanation: The last electron enters the ‘d’ orbital, thus placing it in the d-block.* 9. What tells you the block of the periodic table an element belongs to? a) Number of protons b) Number of neutrons c) Orbital housing the last electron d) Total number of isotopes Answer: c) Orbital housing the last electron *Explanation: The orbital that houses the last electron tells us the block in the periodic table.* 10. Which energy level is filled first, 3d or 4s? a) 3d b) 4s c) They are filled simultaneously d) Depends on the element Answer: b) 4s *Explanation: The 4s orbital is always filled before the 3d orbital.* 11. What is the configuration of an O²⁻ (oxide ion)? a) 1s² 2s² 2p⁴ b) 1s² 2s² 2p⁶ c) 1s² 2s² 2p³ d) 1s² 2s² 2p⁵ Answer: b) 1s² 2s² 2p⁶ *Explanation: Oxide ion (O²⁻) gains two electrons resulting in the configuration 1s² 2s² 2p⁶.* 12. What determines the group number in the periodic table for elements in the s and p blocks? a) Total number of protons b) Number of outer electrons c) Atomic mass d) Number of neutrons Answer: b) Number of outer electrons *Explanation: The total number of electrons in the highest energy level tells us the group number.* 13. What is the configuration of Argon (Ar)? a) 1s² 2s² 2p⁶ 3s² 3p⁶ b) 1s² 2s² 2p⁶ 3s² 3p⁵ c) 1s² 2s² 2p⁶ 3s¹ 3p⁶ d) 1s² 2s² 2p⁶ 3s² Answer: a) 1s² 2s² 2p⁶ 3s² 3p⁶ *Explanation: Argon (Ar) has the configuration 1s² 2s² 2p⁶ 3s² 3p⁶.* 14. Which statement is true? a) Electrons fill lower energy levels first b) Electrons form pairs before filling a new orbital c) Electrons are attracted to each other d) Electrons pair up with the same spin direction Answer: a) Electrons fill lower energy levels first *Explanation: The Aufbau principle states that electrons fill lower energy levels first.* 15. What is the configuration for Al3+ (aluminium ion)? a) 1s² 2s² 2p⁶ 3s² 3p¹ b) 1s² 2s² 2p⁶ c) 1s² 2s² 2p⁶ 3s¹ d) 1s² 2s² 2p³ Answer: b) 1s² 2s² 2p⁶ *Explanation: Aluminium ion (Al³⁺) loses three electrons resulting in the configuration 1s² 2s² 2p⁶.* 16. When filling orbitals, if there are three p orbitals (px, py, pz), how are the electrons distributed initially? a) All three electrons in px b) Two electrons in px, one in py c) One electron in each of px, py, and pz d) Three electrons in px and py Answer: c) One electron in each of px, py, and pz *Explanation: According to Hund’s rule, electrons occupy orbitals singly before pairing up.* 17. What electron configuration does Neon (Ne) have? a) 1s² 2s² 2p⁶ 3s² b) 1s² 2s² 2p⁶ c) 1s² 2s² 2p⁵ d) 1s² 2s² 2p³ Answer: b) 1s² 2s² 2p⁶ *Explanation: Neon (Ne) has the electron configuration 1s² 2s² 2p⁶.* 18. Which element has the electron configuration 1s² 2s² 2p⁶ 3s²? a) Magnesium (Mg) b) Aluminium (Al) c) Silicon (Si) d) Sodium (Na) Answer: a) Magnesium (Mg) *Explanation: Magnesium (Mg) has the electron configuration 1s² 2s² 2p⁶ 3s².* 19. Which noble gas has the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶? a) Helium (He) b) Neon (Ne) c) Argon (Ar) d) Xenon (Xe) Answer: c) Argon (Ar) *Explanation: Argon (Ar) has the configuration 1s² 2s² 2p⁶ 3s² 3p⁶.* 20. If an element has the configuration 1s² 2s² 2p⁶ 3s¹, what is its group number? a) 1 b) 2 c) 3 d) 4 Answer: a) 1 *Explanation: The total number of electrons in the highest energy level (3s¹) tells us it’s in group 1.* 22. What is the electron configuration for calcium ion (Ca²⁺)? a) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² b) 1s² 2s² 2p⁶ c) 1s² 2s² 2p⁶ 3s² 3p⁶ d) 1s² 2s² 2p⁶ 3s² 3p⁵ Answer: c) 1s² 2s² 2p⁶ 3s² 3p⁶ *Explanation: Calcium ion (Ca²⁺) loses two electrons from 4s resulting in 1s² 2s² 2p⁶ 3s² 3p⁶ configuration.* 24. What is the maximum number of electrons that the p subshell can hold? a) 2 b) 6 c) 10 d) 14 Answer: b) 6 *Explanation: The p subshell can hold a maximum of 6 electrons with three orbitals each holding 2 electrons.* 25. Which subshell follows 3d in the electron filling sequence? a) 4p b) 4s c) 5s d) 5p Answer: a) 4p *Explanation: After 3d, electrons fill the 4p subshell next.* 26. Which orbital group has the highest energy level? a) 1s b) 2p c) 3d d) 4p Answer: d) 4p *Explanation: The 4p orbital group has the highest energy level among the listed options.* 27. What does Hund's rule state regarding electron filling in orbitals? a) Electrons fill higher energy levels first b) Electrons fill orbitals singly first before pairing c) Electrons fill with opposite spins d) Electrons pair up in lower energy levels first Answer: b) Electrons fill orbitals singly first before pairing *Explanation: Hund’s rule states that electrons fill orbitals singly first before pairing up.* 28. How many orbitals are present in d subshells? a) 2 b) 3 c) 4 d) 5 Answer: d) 5 *Explanation: The d subshell has five orbitals.* 29. What is the electron configuration for a Phosphorus ion (P³⁻)? a) 1s² 2s² 2p⁶ 3s² 3p³ b) 1s² 2s² 2p⁶ 3s² 3p⁴ c) 1s² 2s² 2p⁶ 3s² 3p⁶ d) 1s² 2s² 2p⁶ 3s² 3p⁵ Answer: c) 1s² 2s² 2p⁶ 3s² 3p⁶ *Explanation: Phosphorus ion (P³⁻) gains three electrons resulting in 1s² 2s² 2p⁶ 3s² 3p⁶ configuration.* 30. Which factor determines the sequence in which electrons fill orbitals? a) Atomic weight b) Energy levels c) Number of neutrons d) Nuclear size Answer: b) Energy levels *Explanation: Electrons fill orbitals from the lowest energy level to the highest.* I hope these questions help enhance your understanding of the detailed atomic structure! Let me know if you need additional practice or explanations.