MTTC MTTC Chemistry 1 — Questions and Answers
Question 1: What is the maximum number of electrons that can occupy the second energy level (n=2) of an atom?
- 2
- 8 (Correct answer)
- 18
- 32
Correct answer: 8
The second energy level holds a maximum of 8 electrons distributed across the 2s² and 2p⁶ subshells.
Question 2: Which element has the highest electronegativity on the Pauling scale?
- Oxygen
- Chlorine
- Fluorine (Correct answer)
- Nitrogen
Correct answer: Fluorine
Fluorine has the highest electronegativity (4.0 on the Pauling scale) of all elements.
Question 3: What type of bond forms when electrons are shared unequally between two atoms of different electronegativities?
- Ionic bond
- Nonpolar covalent bond
- Polar covalent bond (Correct answer)
- Metallic bond
Correct answer: Polar covalent bond
A polar covalent bond results from unequal electron sharing due to an electronegativity difference between bonded atoms.
Question 4: Which quantum number determines the shape of an electron orbital?
- Principal quantum number (n)
- Angular momentum quantum number (l) (Correct answer)
- Magnetic quantum number (ml)
- Spin quantum number (ms)
Correct answer: Angular momentum quantum number (l)
The angular momentum quantum number (l) determines orbital shape, distinguishing s, p, d, and f orbitals.
Question 5: Which pair of atoms represents isotopes of the same element?
- ¹²C and ¹⁴N
- ¹²C and ¹⁴C (Correct answer)
- ¹H and ²He
- ¹⁶O and ³²S
Correct answer: ¹²C and ¹⁴C
¹²C and ¹⁴C are isotopes because both are carbon atoms (same proton count) but differ in neutron count.
Question 6: What is the correct electron configuration for a neutral iron atom (Fe, atomic number 26)?
- [Ar] 3d⁶ 4s² (Correct answer)
- [Ar] 3d⁸
- [Kr] 3d⁶ 4s²
- [Ar] 4d⁶ 4s²
Correct answer: [Ar] 3d⁶ 4s²
Iron's configuration is [Ar] 3d⁶ 4s², as the 4s subshell fills before 3d in the aufbau order.
Question 7: Which statement best describes the trend in atomic radius across a period (left to right) in the periodic table?
- Atomic radius increases because more protons are added
- Atomic radius decreases because nuclear charge increases without adding new energy levels (Correct answer)
- Atomic radius stays constant across a period
- Atomic radius increases because more electrons are added to outer shells
Correct answer: Atomic radius decreases because nuclear charge increases without adding new energy levels
Across a period, increasing nuclear charge pulls electrons closer without adding new energy levels, decreasing atomic radius.
MTTC MTTC Chemistry 1
What is the maximum number of electrons that can occupy the second energy level (n=2) of an atom?