Discovery of Atoms

Atoms are the tiny building blocks that make up everything around us. Ancient philosophers first imagined that everything is made up of small, invisible particles. Over time, scientists conducted experiments that proved these particles, called atoms, really exist. This page will take you on a journey through the history of atomic discovery by closely examining the experiments that revealed the existence of atoms.

    Major Components

    Protons:
    
        Charge: Positive (+1)
    
        Location: Nucleus
    
        Mass: ~1 atomic mass unit (amu)
    
    Neutrons:
    
        Charge: Neutral (0)
        Location: Nucleus
        Mass: ~1 atomic mass unit (amu)
    
    Electrons:
    
        Charge: Negative (-1)
        Location: Electron cloud/orbitals around the nucleus
        Mass: ~1/1836 of a proton (negligible)
    
    Parameters
    Atomic Number (Z):
    
        Number of protons in the nucleus.
        Defines the element and its position in the periodic table.
    
    Mass Number (A):
    
        Sum of protons and neutrons in the nucleus.
        Approximate mass of the atom.
    
    Isotopes:
    
        Atoms of the same element (same atomic number) with different numbers of neutrons (different mass numbers).
    
    Atomic Mass:
    
        Average mass of all isotopes of an element, weighted by their natural abundance.
    
    Energy Levels/Shells:
    
        Electrons occupy different energy levels/shells around the nucleus.
        The first shell can hold up to 2 electrons, the second up to 8, and so on.
    
    Orbitals:
    
        Subdivision of energy levels where electrons are likely to be found.
        Types: s, p, d, f (e.g., 1s, 2p).
    
    Electron Configuration:
    
        Distribution of electrons among the various orbitals.
        Determines chemical behavior.
    
    Valence Electrons:
    
        Electrons in the outermost shell.
        Crucial for chemical bonding and reactions.
    
    Additional Details
    
        Nucleus: Contains protons and neutrons; it's the dense, central part of the atom.
        Electron Cloud: The region around the nucleus where electrons are likely to be found.
        Ionization Energy: The energy required to remove an electron from an atom.
        Electronegativity: A measure of an atom's ability to attract and hold onto electrons.
        Atomic Radius: The distance from the nucleus to the outermost electron shell.