Chemistry Chapter 1: Atoms and Molecules

Learning Objectives

• Atoms and molecules are fundamental topics in chemistry.
• Laws of chemical combination are crucial for understanding chemical reactions.
• Dalton's atomic theory provides a framework for understanding matter and chemical reactions.
• Charged particles (electrons, protons, and neutrons) are vital components of atoms.
• Atomic models explain the structure of atoms.
• Valency, atomic number, mass number, isotopes, and isobars describe atomic properties.
• Molecules and compounds are composed of atoms.
• Ions and molecular mass are essential concepts for understanding chemical compounds.

Discovery of the Atom

• Ancient Indian and Greek philosophers pondered the nature of matter.
• Maharishi Kanad postulated the existence of fundamental particles, which he called Parmanu.
• Pakudha Katyayama elaborated the concept and said these particles existed in combined form.
• Democritus and Leucippus proposed the concept of indivisible particles (atoms).
• Antoine Lavoisier established two important laws of chemical combination, establishing the foundation of modern chemistry.

Laws of Chemical Combination

• Law of Conservation of Mass: Mass is neither created nor destroyed in a chemical reaction. The sum of the masses of reactants equals the sum of the masses of products.
• Law of Constant Proportions: In a chemical compound, the elements are always present in a definite proportion by mass.

Dalton's Atomic Theory

• All matter is composed of atoms, which cannot be created or destroyed.
• Atoms of a given element are identical in mass.
• Atoms of different elements have different masses.
• Atoms combine in simple whole number ratios to form compounds.
• The relative number and kinds of atoms are constant in a given compound.

Atomic Size

• Atoms are incredibly small.
• Atomic radius is measured in nanometers (nm).

Symbols of Elements

• John Dalton introduced symbols for elements.
• Berzelius suggested using one or two letters of the element's name as symbols.
• IUPAC (International Union of Pure and Applied Chemistry) standardized the use of chemical symbols.

IUPAC Nomenclature

• The first letter of a chemical symbol is capitalized, and subsequent letters are lowercase.
• Chemical symbols are derived from Latin, German, or Greek language names of elements.

Atomic Symbols and Numbers

• A table showing the atomic number, symbol, and element name for a selection of elements.