Chemistry Basics: Atoms and Molecules

Learning Objectives

• Atoms and molecules are fundamental topics discussed
• Laws of chemical combination are included
• Dalton's atomic theory is a key concept
• Charged particles in matter (electrons, protons, and neutrons) are covered
• Models of the atom are explored
• Valency, atomic number, mass number, isotopes, and isobars are discussed
• Molecules, molecules of compounds, ions and molecular mass are all important concepts.

Discovery of an Atom

• Ancient Indian and Greek philosophers pondered the unseen form of matter
• Maharishi Kanad postulated that dividing matter leads to smallest particles (Parmanu)
• Pakudha Katyāyana elaborated that these particles exist combined
• Democritus and Leucippus proposed that matter can be divided infinitely until indivisible particles (Atoms)
• Antoine Lavoisier established two important laws of chemical combination

Laws of Chemical Combination

• Two fundamental laws are: Law of Conservation of Mass and Law of Constant Proportions
• Law of Conservation of Mass states that mass is neither created nor destroyed in a chemical reaction
• Law of Constant Proportions states that elements in a chemical compound always combine in a fixed ratio by mass

Dalton's Atomic Theory

• Dalton's atomic theory explains the Law of Conservation of Mass
• Matter consists of small particles called atoms
• Atoms are indivisible and indestructible
• Atoms of the same element are identical in mass and properties
• Atoms of different elements have different masses and properties
• Atoms combine in simple whole-number ratios to form compounds

Size of an Atom

• Atoms are very small, smaller than anything imaginable
• Millions of atoms would only make a thin layer
• Atomic radius is measured in nanometers

Symbols of Elements

• John Dalton was the first to use symbols for elements in a specific way
• A symbol represents a specific quantity of that element (one atom)
• Berzelius proposed using one or two letters from the element's name for symbols
• Element names often derive from the place where they were found

IUPAC Nomenclature

• IUPAC (International Union of Pure and Applied Chemistry) standardizes element names, symbols, and units
• The first letter of a symbol is always uppercase, the second lowercase
• Some symbols are derived from Latin, German, or Greek names

Symbols of Some Elements

• A table providing atomic numbers, symbols, and names of various elements

Name of Element and Latin Name

• A table showing the Latin names and symbols of various elements

This quiz covers fundamental concepts in chemistry, focusing on atoms, molecules, and the laws of chemical combination. Explore key topics such as Dalton's atomic theory, valency, and the definitions of atomic number and mass number. Test your knowledge on the historical perspectives of atomic theory and the contributions from ancient philosophers.