Atom And Molecules Class 9 Pdf Download [better] 📍

All matter is made of very tiny particles called atoms.Atoms are indivisible particles that cannot be created or destroyed.Atoms of a given element are identical in mass and chemical properties.Atoms of different elements have different masses and chemical properties.Atoms combine in the ratio of small whole numbers to form compounds. What is an Atom?

Molecules of Elements: These contain atoms of the same type, such as O2 (Oxygen) or P4 (Phosphorus).Molecules of Compounds: These consist of atoms of different elements joining in definite proportions, such as H2O (Water) or CO2 (Carbon Dioxide). Ions and Chemical Formulae atom and molecules class 9 pdf download

Atoms or groups of atoms with a net charge are called ions. Negatively charged ions are anions, while positively charged ions are cations. To write a chemical formula, one must know the symbols and valency (combining capacity) of the elements involved. By "criss-crossing" the valencies, the formula is derived. For example, Magnesium Chloride is written as MgCl2. Molecular Mass and Mole Concept All matter is made of very tiny particles called atoms

Before the discovery of subatomic particles, scientists established laws based on chemical reactions. Ions and Chemical Formulae Atoms or groups of

Law of Conservation of Mass: Mass can neither be created nor destroyed in a chemical reaction. The total mass of reactants always equals the total mass of products.Law of Constant Proportions: In a chemical substance, elements are always present in definite proportions by mass, regardless of the source or method of preparation. Dalton's Atomic Theory