পারমাণবিক গঠন ও পরমাণু সারণী

Atomic Structure

• Atoms are the fundamental building blocks of matter, composed of a nucleus containing protons and neutrons, surrounded by electrons.
• Protons have a positive charge, neutrons are neutral, and electrons have a negative charge.
• The number of protons in an atom determines its atomic number, defining the element.
• Atoms can gain or lose electrons to form ions.
• Isotopes are atoms of the same element with different numbers of neutrons.
• Atomic mass is the weighted average of the masses of all isotopes of an element.

Periodic Table

• The periodic table arranges elements by increasing atomic number, revealing periodic trends in their properties.
• Elements are grouped into families (or columns) based on similar chemical properties.
• Elements in a period (or row) show increasing metallic character as you move left to right.
• Metals are generally good conductors of heat and electricity, losing electrons to form positive ions.
• Nonmetals are generally poor conductors and tend to gain electrons forming negative ions.
• Metalloids exhibit properties intermediate between metals and nonmetals.

Bonding

• Chemical bonds hold atoms together in molecules and compounds.
• Ionic bonds form between a metal and a nonmetal, involving electron transfer.
• Covalent bonds form between nonmetals, sharing electrons.
• Metallic bonds are unique to metals, featuring delocalized electrons.
• Polar covalent bonds occur when electrons are shared unequally creating slight positive and negative charges.

Chemical Reactions

• Chemical reactions involve the rearrangement of atoms to form new substances.
• Reactants are the substances undergoing change, while products are the substances formed.
• Chemical equations represent the transformation of reactants to products, with balanced atoms on both sides.
• Chemical reactions can be classified into various types based on the processes involved.
• Exothermic reactions release energy, while endothermic reactions absorb energy.
• Factors like temperature, concentration, and pressure affect reaction rates.

States of Matter

• Matter exists in three primary states: solid, liquid, and gas.
• Solids have a definite shape and volume.
• Liquids have a definite volume but take the shape of their container.
• Gases have neither a definite shape nor volume.
• Phase changes are transitions between these states, involving energy absorption or release.

Stoichiometry

• Stoichiometry is the quantitative study of reactants and products in chemical reactions.
• The mole concept is crucial in calculating quantities in chemical reactions.
• Stoichiometric calculations relate reactant and product amounts using balanced equations, molar masses, and mole ratios.
• Calculations include determining limiting reagents, percent yield, and theoretical yield.

Acids and Bases

• Acids release hydrogen ions (H+) in solution, while bases release hydroxide ions (OH−) in solution.
• The pH scale measures the acidity or basicity of a solution.
• Strong acids and bases completely dissociate in water; weak acids and bases partially dissociate.
• Neutralization reactions occur when an acid reacts with a base to form a salt and water.

Redox Reactions

• Oxidation-reduction (redox) reactions involve electron transfer between reactants.
• Oxidation is the loss of electrons, while reduction is the gain of electrons.
• Oxidation numbers track electron transfer in redox reactions.
• Oxidizing agents cause oxidation; reducing agents cause reduction.

Solutions

• Solutions are homogeneous mixtures of two or more substances.
• Solvents are the major component; solutes are the minor components.
• Solubility describes a substance's ability to dissolve in a solvent.
• Solution concentration is expressed in various ways (e.g., molarity, molality, percentage).