Question: What is the atomic number of an element that has 16 protons? Solution: The atomic number is 16.
Question: How many neutrons does an atom of Carbon-14 (¹⁴C) have? Solution: The atom has 8 neutrons (14 – 6 = 8).
Question: Identify the isotope with 17 protons and 18 neutrons. Solution: This isotope is Chlorine-35 (³⁵Cl).
Question: Which subatomic particle determines the chemical behavior of an atom? Solution: The electrons determine the chemical behavior of an atom.
Question: Which rule states that electrons fill lower energy orbitals first? Solution: This is the Aufbau principle.
Question: An atom of ²³⁸U undergoes α-decay. What is the atomic number and mass number of the resulting atom? Solution: The resulting atom is ²³⁴Th with an atomic number of 90 (92 – 2 = 90) and a mass number of 234 (238 – 4 = 234).
Question: How many valence electrons does an atom of sulfur (S) have? Solution: Sulfur has 6 valence electrons.
Question: What is the maximum number of electrons that can be held in the second energy level (n=2)? Solution: The second energy level can hold a maximum of 8 electrons.
Question: What does A stand for in the isotope notation AᵢZ? Solution: A stands for the mass number (the total number of protons and neutrons).
Question: Which atomic model introduced the concept of quantum energy levels? Solution: The Bohr model introduced this concept.
Question: Name the scientist who discovered the electron. Solution: J.J. Thomson discovered the electron.
Question: What is the charge of a neutron? Solution: The neutron has no charge; it is neutral.
Question: How many electrons can a single orbital hold? Solution: A single orbital can hold a maximum of 2 electrons.
Question: What is the atomic mass of an atom with 20 protons, 20 electrons, and 21 neutrons? Solution: The atomic mass is 41 amu (20 protons + 21 neutrons = 41).
Question: What are isotopes? Solution: Isotopes are atoms of the same element with different numbers of neutrons, and hence different mass numbers.
Question: Which principle states that it’s impossible to simultaneously measure both the position and momentum of an electron with absolute precision? Solution: This is the Heisenberg Uncertainty Principle.
Question: An atom of ²⁴Mg²⁺ loses two electrons. What is the atomic number of the resulting ion? Solution: The atomic number is 12, which doesn’t change with the loss or gain of electrons.
Question: Which subatomic particle contributes to the mass of the atom but not to its charge? Solution: The neutron contributes to the mass of the atom but not to its charge.
Question: Which theory proposed that atoms of the same element can have different masses? Solution: Dalton’s Atomic Theory was the first to propose this, later leading to the concept of isotopes.
Question: If the electron configuration of an atom is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹, which element is it? Solution: The atom is Potassium (K).