Atomic Structure and Conductors
An atom has protons (+ charge) and neutrons in the nucleus, and electrons (− charge) orbiting in shells. The outermost shell is the valence shell. Valence electrons can move between atoms — this movement is electric current.
- Conductors (copper, silver): 1–3 valence electrons; electrons move freely.
- Insulators (rubber, glass): 5–8 valence electrons; electrons are tightly bound.
- Semiconductors (silicon, germanium): exactly 4 valence electrons — between conductor and insulator; the basis of transistors and diodes.
Atomic number = number of protons. A neutral atom has equal protons and electrons.