Overview
This lecture reviews basic atomic structure, focusing on the components of the atom, their properties, forces within atoms, and concepts concerning ions.
Structure of the Atom
- Atoms have a central nucleus containing protons and neutrons.
- Electrons are found outside the nucleus, forming the electron cloud.
- The atom is mostly empty space; the nucleus is much smaller than the electron cloud.
- 99% of an atom's mass is concentrated in the nucleus.
Subatomic Particles and Charges
- Protons have a positive charge and are found in the nucleus.
- Neutrons are electrically neutral and also in the nucleus.
- Electrons have a negative charge and orbit the nucleus.
- Opposite charges attract, so electrons are attracted to the nucleus.
Why Electrons Stay in Orbit
- Electrons are kept in orbit by a balance of their speed (tangential velocity) and electrostatic attraction to protons.
- Electrons can escape the atom if they gain enough energy, becoming ions.
- Electron capture is when an electron falls into the nucleus, changing the element.
Forces Within the Nucleus
- Protons repel each other due to like charges, but the strong nuclear force keeps the nucleus together.
- The strong nuclear force is much stronger than the electrostatic force.
Mass of Subatomic Particles
- Neutrons are slightly heavier than protons.
- Both protons and neutrons have a mass of approximately 1 atomic mass unit (amu).
- The electron’s mass is negligible (~0.000549 amu).
Atoms vs. Ions and Net Charge
- Atoms are electrically neutral with equal numbers of protons and electrons.
- An ion has unequal numbers of protons and electrons, resulting in a net charge.
- The net charge equals the number of protons minus the number of electrons.
- A cation is a positively charged ion; an anion is a negatively charged ion.
- Ions do not necessarily have equal numbers of protons and neutrons.
Key Terms & Definitions
- Electron — negatively charged particle orbiting the nucleus.
- Proton — positively charged particle in the nucleus.
- Neutron — electrically neutral particle in the nucleus.
- Nucleus — central core of the atom containing protons and neutrons.
- Ion — atom with unequal numbers of protons and electrons, carrying a net charge.
- Cation — positively charged ion.
- Anion — negatively charged ion.
- Strong nuclear force — force holding protons and neutrons together in the nucleus.
Action Items / Next Steps
- Review key definitions and mass/charge properties of atomic particles.
- Practice calculations of net charge for atoms and ions.
- Look up electron capture for further understanding.