Hello friends! These are some short notes on atoms and molecules for 9th & 10th class students.
Atoms and molecules are responsible to make everything like dust, sand, ink, bricks, buildings, mobile in your hands, humans, animals, plants. Everything is made up of atoms. Atom is basic fundamental unit of matter. When atoms bond together they form molecules.
Atoms
We can simply say that Atom is basic building block of all matters. Atom have nucleus, which is very small and heaviest part of the atom. Atom is surrounded by large cloud of electrons, which is lightest part of the atom.
Definition: The smallest unit of an element that retains its chemical properties.
Structure: Composed of protons, neutrons, and electrons.
Protons: Positively charged particles found in the nucleus.
Neutrons: Neutral particles also found in the nucleus.
Electrons: Negatively charged particles orbiting the nucleus.
Atomic Number: The number of protons in an atom’s nucleus, which defines the element.
Mass Number: The total number of protons and neutrons in the nucleus.
Atom
Molecules
We can simply say that, when two or more than two atoms form bond with each other they form a molecule. A group of atoms held together by chemical bonds.
Definition: The smallest unit of a compound that retains its chemical properties.
Formation: Atoms bond together to form molecules.
Types of Bonds:
Covalent Bonds: Atoms share electrons.
Ionic Bonds: Atoms transfer electrons, resulting in charged ions that attract each other.
Examples:
Oxygen Molecule (O₂): Two oxygen atoms bonded together.
Water Molecule (H₂O): Two hydrogen atoms and one oxygen atom bonded together.
Laws of Chemical Combination
Law of Conservation of Mass: Mass is neither created nor destroyed in a chemical reaction.
Law of Constant Proportion: A chemical compound always contains the same elements in the same proportion by mass.
Dalton’s Atomic Theory
John Dalton was an English chemist, physicist, and meteorologist. He developed modern atomic theory.
Matter is made up of tiny 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.
Some Important Terminology from chapter Atom and Molecule
Atomic Mass: The mass of an atom, typically measured in atomic mass units (amu).
Molecular Mass: The sum of the atomic masses of all atoms in a molecule.
Mole Concept: A mole is a unit that measures the amount of substance, defined as containing exactly (6.022 x 10^{23}) particles (Avogadro’s number).
Do you know! “What is viscosity in chemistry". To understand about viscosity, we take example of some liquids like Honey and Water. As we know honey is thicker than water. So, honey flow with very slow speed on floor than water, as water is very less thick, so it flows quickly... Learn more...
