Atomic Structure Basics
Understanding atoms is like learning the building blocks of everything around you. Atoms contain three key particles: protons (positive charge, mass of 1), neutrons (no charge, mass of 1), and electrons (negative charge, virtually no mass).
The nucleus sits at the centre, packed with protons and neutrons, giving it a positive charge overall. Electrons whiz around this nucleus in shells or energy levels. Here's the crucial bit: atoms are normally neutral because they have equal numbers of protons and electrons.
Ions are different though - they're atoms that have gained or lost electrons, giving them an overall charge. The atomic number tells you how many protons an atom has, whilst the mass number is protons plus neutrons. So if you need to find neutrons, just subtract atomic number from mass number.
Quick Check: Atoms are absolutely tiny - about 0.1 nanometres across (that's 0.0000000001 metres!).