# Atomic structure problems and solutions

1. Question: What is the atomic number of an element with 8 protons? Solution: The atomic number is 8.

2. Question: How many protons are in an atom of Fluorine-19 (¹⁹F)? Solution: The atom has 9 protons.
3. Question: Identify the isotope with 6 protons and 8 neutrons. Solution: This isotope is Carbon-14 (¹⁴C).
4. Question: Which subatomic particle affects the atomic mass but not the chemical properties of an atom? Solution: The neutrons affect the atomic mass but not the chemical properties of an atom.
5. Question: What is the mass number of an atom that has 20 protons, 20 neutrons, and 20 electrons? Solution: The mass number is 40 (20 protons + 20 neutrons = 40).
6. Question: An atom of ²²⁶Ra undergoes α-decay. What is the atomic number and mass number of the resulting atom? Solution: The resulting atom is ²²²Rn with an atomic number of 86 (88 – 2 = 86) and a mass number of 222 (226 – 4 = 222).
7. Question: How many valence electrons does an atom of nitrogen (N) have? Solution: Nitrogen has 5 valence electrons.
8. Question: What is the maximum number of electrons that can be held in the third energy level (n=3)? Solution: The third energy level can hold a maximum of 18 electrons.
9. Question: What does Z represent in the isotope notation AᵢZ? Solution: Z stands for the atomic number (the total number of protons).
10. Question: Which atomic model was proposed by Erwin Schrödinger? Solution: The quantum mechanical model (or the electron cloud model) was proposed by Schrödinger.
11. Question: Name the scientist who proposed the planetary model of an atom. Solution: Niels Bohr proposed the planetary model of an atom.
12. Question: What is the charge of a proton? Solution: The proton has a positive charge.
13. Question: How many orbitals are in the p sublevel? Solution: There are 3 orbitals in the p sublevel.
14. Question: What is the total charge of an atom with 13 protons, 14 neutrons, and 13 electrons? Solution: The total charge is 0, as the number of protons (positive charge) and electrons (negative charge) are equal.
15. Question: What are energy levels? Solution: Energy levels are the fixed energies an electron can have within an atom.
16. Question: Which principle states that electrons will occupy the most stable (lowest energy) orbital available? Solution: This is the Aufbau Principle.
17. Question: An ion of ²⁷Al³⁺ gains three electrons. What is the atomic number of the resulting atom? Solution: The atomic number is 13, which doesn’t change with the loss or gain of electrons.
18. Question: What is the mass number of an atom with 18 protons and 22 neutrons? Solution: The mass number is 40 (18 protons + 22 neutrons = 40).