Atomic Theory and Building Blocks

Atomic Theory

• Atoms are the fundamental building blocks of matter
• Dalton's Atomic Theory provided early evidence of atoms

Atomic Building Blocks

• Atoms consist of protons (positive charge), electrons (negative charge), and neutrons (no charge)
• Protons and neutrons are in the atom's nucleus
• Electrons orbit the nucleus

Elements and Nuclides

• Elements are identified by their atomic number (number of protons)
• All atoms of an element have the same number of protons
• Isotopes are nuclides of an element with different numbers of neutrons
• Each nuclide has a specific atomic number and mass number

Substances and Mixtures

• Matter can be classified into pure substances (elements and compounds) and mixtures
• Pure substances have a fixed ratio of atoms
• Elements contain only one type of atom
• Compounds contain two or more types of atoms
• Mixtures can be homogeneous or heterogeneous
• Homogeneous mixtures have uniform composition
• Heterogeneous mixtures show visible differences in composition

Physical and Chemical Properties

• Substances have physical and chemical properties
• Physical properties can be observed without altering the substance's identity
• Chemical properties describe how a substance reacts with other substances, changing its identity

Energy

• Energy is the ability to do work
• Energy can be converted from one form to another
• Energy can be stored in atomic configurations (chemical energy) or associated with motion (thermal energy)
• Exothermic processes release heat
• Endothermic processes absorb heat
• Exergonic processes release energy
• Endergonic processes require energy input