Overview
This lecture explains atomic structure, chemical symbols, and how to determine atomic particles, isotopes, and ions using the periodic table.
Atomic Structure
- Atoms are composed of three particles: protons (positive), neutrons (neutral), and electrons (negative).
- John Dalton theorized that everything is made of atoms.
- Protons and neutrons are located in the nucleus; electrons orbit the nucleus.
Chemical Symbols and Notation
- A chemical symbol is written as ( ^A_ZX ), where X is the element, A is the mass number, and Z is the atomic number.
- The atomic number (Z) equals the number of protons in the atom.
- The mass number (A) equals the sum of protons and neutrons.
Atomic Mass vs. Mass Number
- Mass number (A) is the total of protons and neutrons for a single atom.
- Atomic mass is the weighted average of all isotopes of that element.
Determining Subatomic Particles
- In neutral atoms, the number of protons equals the number of electrons.
- Number of neutrons = mass number (A) minus atomic number (Z).
- Protons and atomic number are always the same.
Ions and Their Charges
- Ions are atoms with a net charge due to unequal protons and electrons.
- Negative ions (anions) have more electrons than protons; positive ions (cations) have fewer electrons.
- For a negative charge, electrons = protons + charge.
- For a positive charge, electrons = protons - charge.
Examples and Problem Solving
- For phosphorus (( ^{31}_{15}P^{3-} )), protons = 15, neutrons = 16, electrons = 18.
- For phosphorus (( ^{31}_{15}P^{3+} )), protons = 15, neutrons = 16, electrons = 12.
- Iron with 26 protons, 30 neutrons, and 29 electrons is an ion (( Fe^{3-} )), not neutral.
Determining Neutral vs. Ion
- If protons = electrons, the atom is neutral.
- If protons ≠ electrons, the atom is an ion.
Key Terms & Definitions
- Atom — smallest unit of matter with unique chemical properties.
- Proton — positively charged subatomic particle in the nucleus.
- Neutron — neutral subatomic particle in the nucleus.
- Electron — negatively charged subatomic particle orbiting the nucleus.
- Atomic number (Z) — number of protons in an atom.
- Mass number (A) — total number of protons and neutrons.
- Atomic mass — average mass of all isotopes of an element.
- Ion — atom with unequal numbers of protons and electrons, carrying a charge.
- Isotope — atoms of the same element with different numbers of neutrons.
Action Items / Next Steps
- Complete linked practice problems with step-by-step answers.
- Leave questions or homework problems in the comments for help.