BMST Atomic Structure and Bonding 5 — Questions and Answers
Question 1: What does the principal quantum number (n) describe?
- The shape of the orbital
- The energy level or shell of an electron (Correct answer)
- The spin of an electron
- The magnetic orientation of an orbital
Correct answer: The energy level or shell of an electron
The principal quantum number n indicates the main energy level (shell) where an electron is found.
Question 2: A coordinate covalent bond differs from a regular covalent bond because:
- It involves metal atoms only
- Both electrons are contributed by the same atom (Correct answer)
- It transfers electrons permanently
- It only forms in water
Correct answer: Both electrons are contributed by the same atom
In a coordinate (dative) covalent bond, one atom donates both electrons of the shared pair.
Question 3: Which element has atomic number 6 and is the basis of organic chemistry?
- Nitrogen
- Oxygen
- Carbon (Correct answer)
- Silicon
Correct answer: Carbon
Carbon has atomic number 6 and its ability to form four bonds makes it the backbone of organic molecules.
Question 4: When an atom gains an electron, it becomes a(n):
- Cation
- Anion (Correct answer)
- Isotope
- Neutral atom
Correct answer: Anion
Gaining an electron gives the atom a net negative charge, making it a negatively charged ion called an anion.
Question 5: Which subshell fills first: 3d or 4s?
- 3d fills first
- 4s fills first (Correct answer)
- They fill simultaneously
- It depends on the element
Correct answer: 4s fills first
According to the Aufbau principle, 4s has lower energy than 3d and fills before it in electron configuration.
Question 6: The bond angle in a water molecule (H₂O) is approximately:
- 180°
- 120°
- 109.5°
- 104.5° (Correct answer)
Correct answer: 104.5°
Water's bond angle is about 104.5° because two lone pairs on oxygen repel the bonding pairs, compressing the angle.
Question 7: Which of the following is an example of an ionic compound?
- H₂O
- CO₂
- NaCl (Correct answer)
- CH₄
Correct answer: NaCl
NaCl (table salt) is an ionic compound formed by the transfer of an electron from sodium to chlorine.
BMST Atomic Structure and Bonding 5
What does the principal quantum number (n) describe?