TEAS® Science Study Guide
Atomic Structure
An atom has three particles.
|
Particle |
Charge |
Location |
Role |
|
Proton |
Positive (+) |
Nucleus |
Defines the element |
|
Neutron |
Neutral (0) |
Nucleus |
Adds mass |
|
Electron |
Negative (−) |
Orbits nucleus |
Forms bonds |
Two numbers that matter
- Atomic number = number of protons. This defines the element — every carbon atom has 6 protons, always.
- Mass number = protons + neutrons.
Variations of an atom
- Isotopes — Same element, different number of neutrons (so different mass). Same protons, though.
- Ions — Atoms that have gained or lost electrons, giving them a charge. Lose electrons → positive (cation). Gain electrons → negative (anion).
Electrons and bonding
Electrons occupy shells around the nucleus. The outermost electrons — valence electrons — determine how an atom bonds. Atoms are most stable with a full outer shell (usually 8 electrons), which drives nearly all chemical bonding.
Terms to know
- Nucleus — The atom’s dense center; holds protons and neutrons.
- Valence electrons — Outer-shell electrons that control bonding.
- Ion — A charged atom.
- Isotope — Same element, different neutron count.
What the TEAS asks most
- Which particle defines the element? Proton (atomic number).
- What’s the charge of an electron? Negative.
- What are isotopes? Same element, different number of neutrons.
- What determines how an atom bonds? Valence electrons.