1. What occurs when electrons fill an orbital with opposite spins according to Pauli’s exclusion principle?

A. The orbital becomes unstable B. The orbital becomes full and stable C. The orbital only holds one electron D. The orbital is empty

2. What does the atomic number of an atom represent?

A. Number of neutrons B. Number of electrons only C. Number of protons D. Number of protons plus neutrons

3. How are electrons arranged in an atom?

A. Randomly spread throughout the atom B. Orbit the nucleus in defined orbitals or clouds C. Fixed only in the nucleus with protons and neutrons D. Only move outside the atom

4. How many electrons can occupy the p subshell?

A. 2 B. 6 C. 10 D. 14

5. What does the formula \(2[\; 2l + 1\;]\) represent?

A. The number of orbitals in a subshell of angular momentum quantum number \(l\) B. The maximum number of electrons in an orbital C. Number of electrons in outer shell D. Weighted atomic mass formula

6. What does the Aufbau principle state about electron configuration?

A. Electrons fill orbitals with the highest energy first B. Electrons fill orbitals randomly C. Electrons fill orbitals in order of increasing energy D. Electrons only fill orbitals in pairs

7. What is the typical maximum number of electrons in the fourth energy level (N shell)?

A. 8 B. 18 C. 32 D. 50

8. What is the main contribution of Erwin Schrödinger’s atomic model?

A. Electrons revolve around the nucleus in fixed orbits B. Electrons have fixed paths and locations C. Electrons exist in probability clouds rather than exact orbits D. Atoms combine to form molecules

9. What explains why electrons do not follow classical orbits?

A. Heisenberg’s uncertainty principle B. Hund’s rule C. Aufbau principle D. Pauli exclusion principle

10. What principle states that electrons enter orbitals with the lowest energy first?

A. Hund’s rule B. Pauli exclusion principle C. Aufbau principle D. Heisenberg uncertainty principle

11. What is the shape of d orbitals?

A. Spherical B. Dumb-bell C. Double dumb-bell with directional characteristics D. Cube

12. In the electron cloud model, the shape of the orbital depends on:

A. The proton number B. The type of sub-shell (s, p, d) C. The number of neutrons D. The electron spin

13. Why do isotopes of the same element have similar chemical properties?

A. They have the same mass number B. They have the same number of neutrons C. They have the same atomic number and electron arrangement D. They have different numbers of electrons

14. Which shape corresponds to p orbitals?

A. Spherical B. Dumb-bell C. Circular D. Double dumb-bell

15. What defines an atom of an element?

A. A group of molecules with the same mass B. The smallest part of an element that still retains its properties C. A proton and neutron combined D. An electron in a cloud

16. What do isotopes of an element differ in?

A. Number of protons B. Number of electrons C. Number of neutrons D. Chemical properties

17. What is the charge of a proton?

A. -1 B. 0 C. +1 D. +2

18. How many quarks make up a proton or neutron?

A. 1 B. 2 C. 3 D. 6

19. What does the Pauli exclusion principle state?

A. Only one electron can occupy an orbital at a time B. Only electrons with opposite spins can share the same orbital C. Electrons always occupy orbitals with the lowest energy D. Electrons must have the same spin in degenerate orbitals

20. What is the main limitation of the Bohr atomic model described in the document?

A. It fails to explain the nucleus B. It describes electrons moving in fixed orbits which is inaccurate C. It does not include protons D. It treats electrons as particles only without wave properties

21. What is the charge of an electron?

A. +1 B. 0 C. -1 D. +2

22. What is the minimum number of electrons per orbital according to Hund’s rule before pairing occurs?

A. Zero B. One C. Two D. Three

23. How was the electron discovered according to the document?

A. By Democritus and Dalton’s theories B. J.J. Thomson by cathode ray tube experiments C. Rutherford’s gold foil experiment D. Bohr’s planetary model

24. An atom loses electrons to form what?

A. Isotopes B. Ions C. Molecules D. Neutrons

25. What is the primary use of scaled-up atomic models?

A. Visualize extremely small particles like atoms B. Measure atomic mass directly C. Change atomic structure D. Predict chemical reactions

26. How are orbitals related to energy levels?

A. Orbitals define the shape of specific regions within an energy level where electrons are likely found B. Orbitals contain the nucleus C. Orbitals are only in the first energy level D. Orbitals hold protons and neutrons

27. Which statement is true regarding the atomic mass unit (amu)?

A. Protons and neutrons have mass ~1 amu, electrons much less B. Electrons have mass equal to protons C. Neutrons have no mass D. Amu is the charge of the proton

28. What characteristic differentiates isotopes of the same element?

A. Number of protons B. Number of electrons C. Number of neutrons D. Number of valence electrons

29. According to Hund’s rule, how do electrons fill degenerate orbitals within the same subshell?

A. Electrons pair up immediately in the first orbital before occupying others B. Electrons occupy orbitals randomly regardless of spin C. Electrons enter each degenerate orbital singly with parallel spins before pairing occurs D. Electrons fill orbitals with the highest energy first

30. According to Hund’s rule, how do electrons fill degenerate orbitals?

A. They pair up immediately B. They enter singly and with parallel spin as much as possible before pairing C. They enter the orbital with the highest energy first D. They fill each orbital with opposite spins simultaneously

31. What shape is associated with p orbitals?

A. Spherical B. Dumbbell-shaped C. Double dumb-bell with directional characteristics D. Circular ring

32. What is the maximum number of electrons the third energy level can hold?

A. 2 B. 8 C. 18 D. 32

33. Why is the average atomic mass usually closest to the mass of the most abundant isotope?

A. Because the most abundant isotope has the highest energy B. Because the average is weighted according to the abundance of each isotope C. Because all isotopes have the same mass D. Because the least abundant isotopes do not contribute to atomic mass

34. How is average atomic mass calculated?

A. By adding isotopes’ mass numbers B. By calculating the weighted average of the isotopes’ masses based on abundance C. By multiplying atomic number by mass number D. By subtracting number of neutrons from atomic number

35. According to the Aufbau principle, which orbital fills after 1s?

A. 2s B. 2p C. 3s D. 2d

36. What shape is associated with s orbitals?

A. Dumb-bell B. Double dumb-bell C. Spherical D. Cubic

37. Which of the following statements is true about isotopes?

A. They have the same number of neutrons but different electrons B. They have the same atomic number but different mass numbers C. They have different atomic numbers and mass numbers D. They have different chemical properties

38. Which subatomic particles are found in the nucleus of an atom?

A. Electrons only B. Protons and electrons C. Protons and neutrons D. Neutrons and electrons

39. What formula expresses the maximum number of electrons in an energy shell?

A. \(2n^2\) B. \(n^2\) C. \(2n\) D. \(n\)

40. What is an isotope identified by?

A. Its chemical symbol and number of protons B. Its chemical symbol and number of electrons C. Its element name followed by its mass number D. Its element name followed by atomic number

41. What is the relative atomic mass of a sample with 70% copper-63 and 30% copper-65?

A. 63.0 amu B. 64.2 amu C. 63.6 amu D. 65.0 amu

42. Which statement is correct about valence electrons?

A. Electrons in the innermost shell B. Electrons in the nucleus C. Electrons in the outermost energy level D. All electrons in the atom

43. What is the charge of a neutron?

A. +1 B. 0 (neutral) C. -1 D. +2

44. What principle prevents two electrons in the same orbital from having identical quantum states?

A. Hund’s rule B. Aufbau principle C. Pauli exclusion principle D. Heisenberg uncertainty principle

45. How many electrons can the third energy level (M shell) hold according to the document?

A. 8 electrons B. 18 electrons C. 32 electrons D. 50 electrons

46. What does the quantum number \(n\) represent?

A. Electron spin B. Energy level or shell number C. Orbital shape D. Number of protons in nucleus

47. Which subatomic particle has nearly negligible mass compared to protons and neutrons?

A. Proton B. Neutron C. Electron D. Quark

48. What is the mass number of an atom?

A. The number of protons only B. The number of neutrons only C. The sum of protons and neutrons D. The number of electrons

49. How many electrons can an s orbital hold?

A. 1 B. 2 C. 4 D. 8

50. According to Schrödinger’s atomic model, what do orbitals represent?

A. Fixed paths where electrons travel B. Specific points where electrons are located C. Regions of probability where an electron is likely found D. The nucleus of the atom