Fundamentals of Atomic Structure

Overview

• Topic: Basics of atoms and atomic structure for TEAS exam preparation.
• Purpose: Provide clear, foundational concepts students must memorize for common TEAS chemistry questions.
• Scope: Definitions of atoms/elements, subatomic particles, nucleus, charges, masses, electron arrangement, valence electrons, and sample practice questions.

Atoms and Elements

• Atoms are tiny particles that make up all matter.
• Different types of atoms are called elements (e.g., copper, hydrogen, oxygen, sodium, chlorine).
• Atoms can form molecules or crystalline grids depending on arrangement.

Atomic Structure

• Atoms contain smaller subatomic particles: protons, neutrons, and electrons.
• Protons and neutrons are located in the nucleus (center of the atom).
• Electrons move outside the nucleus in regions called energy levels or shells.

Subatomic Particles: Key Properties

• Proton
  • Charge: +1
  • Mass: 1 AMU (atomic mass unit)
  • Location: nucleus
• Neutron
  • Charge: 0 (neutral)
  • Mass: 1 AMU
  • Location: nucleus
• Electron
  • Charge: -1
  • Mass: ~0 AMU (negligible compared to protons/neutrons)
  • Location: outside nucleus, in energy levels/shells

Table: Subatomic Particle Summary

Electrons and Energy Levels

• Electrons are always in motion, not fixed in place.
• Electrons are organized into energy levels (shells).
• Outermost energy level = valence level (valence shell).
• Electrons in the valence shell = valence electrons.
• Valence electrons determine chemical bonding behavior.

Simplified Model for TEAS

• TEAS usually uses the older shell model (circular energy levels).
• More advanced concepts (orbitals, s/p/d/f, electron clouds) are rarely required for TEAS.
• Focus study on the simple shell model and valence electrons rather than detailed quantum orbitals.

Practice Questions Covered

• Identify false statement about subatomic particles:
  • Incorrect example: "An electron has a mass of 1 AMU" (false; electron mass ≈ 0 AMU).
• Label parts of an atomic diagram:
  • Neutral particle in nucleus = neutron.
  • Positive particle in nucleus = proton.
  • Negative particle outside nucleus = electron.
  • Outermost shell = valence shell.
• Determine valence electrons from a diagram:
  • Count electrons in outermost shell; example answer given was one valence electron.

Key Terms and Definitions

• Atom: Basic unit of matter.
• Element: Type of atom defined by proton count.
• Nucleus: Central region containing protons and neutrons.
• Proton: Positively charged subatomic particle (+1).
• Neutron: Neutral subatomic particle (0 charge).
• Electron: Negatively charged subatomic particle (-1).
• AMU: Atomic mass unit, used for proton/neutron masses.
• Energy Level/Shell: Region where electrons are found.
• Valence Shell/Valence Electrons: Outermost shell and its electrons; important for bonding.

Action Items / Next Steps

• Memorize charges and masses of protons, neutrons, electrons.
• Practice identifying nucleus, protons, neutrons, electrons on diagrams.
• Practice counting valence electrons from various atomic diagrams.
• Proceed to next lesson: deeper look at protons and atomic number.