Basic Concepts of Chemistry

Atoms: The fundamental units of matter, 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 that orbit the nucleus.
Elements: Pure substances made of only one type of atom; organized in the periodic table.
- Each element has a unique atomic number (number of protons).
Compounds: Substances formed from two or more different elements bonded together (e.g., H2O).

Ionic Bonds: Formed when one atom transfers electrons to another, resulting in oppositely charged ions.
Covalent Bonds: Formed when two atoms share electrons.
Metallic Bonds: A bond formed by the attraction between positively charged metal ions and delocalized electrons.

Solid: Definite shape and volume; particles tightly packed.
Liquid: Definite volume but takes the shape of its container; particles are close but can move past each other.
Gas: No definite shape or volume; particles are far apart and move freely.

Reactants: Substances that undergo change in a chemical reaction.
Products: New substances formed as a result of the chemical reaction.
Types of Reactions:
- Synthesis: A + B → AB
- Decomposition: AB → A + B
- Single Replacement: A + BC → AC + B
- Double Replacement: AB + CD → AD + CB
- Combustion: Hydrocarbon + O₂ → CO₂ + H₂O

Mole: A unit for measuring amount of substance; can be used to convert between atoms, molecules, and mass.
Avogadro's Number: 6.022 x 10²³ particles per mole.
Molar Mass: The mass of one mole of a substance, usually expressed in grams per mole.

Acids: Substances that donate protons (H⁺ ions) in solution; turn blue litmus paper red.
Bases: Substances that accept protons or donate hydroxide ions (OH⁻) in solution; turn red litmus paper blue.
pH Scale: Measures the acidity or basicity of a solution (scale from 0 to 14); 7 is neutral.

Exothermic Reactions: Release heat; products have lower energy than reactants.
Endothermic Reactions: Absorb heat; products have higher energy than reactants.
Activation Energy: The minimum energy required for a reaction to occur.

Groups: Vertical columns; elements share similar chemical properties.
Periods: Horizontal rows; indicate the number of electron shells.
Metals, Nonmetals, and Metalloids: Classification based on physical and chemical properties.

Atomic Theory: All matter is composed of atoms; atoms of a given element are identical.
Kinetic Molecular Theory: Explains the behavior of gases in terms of particle motion.

The smallest unit of matter is the atom.
Atoms are made up of protons, neutrons, and electrons.
Protons are positively charged and reside in the nucleus.
Neutrons are neutral and also reside in the nucleus.
Electrons are negatively charged and orbit the nucleus.
Elements are pure substances composed of only one type of atom.
The periodic table is a chart that organizes all known elements.
Each element has a unique atomic number, which represents the number of protons in its atom.
Compounds are substances formed when two or more different elements are chemically bonded together.

There are three major types of chemical bonds: ionic, covalent, and metallic.
Ionic bonds form when atoms transfer electrons, creating oppositely charged ions that are attracted to each other.
Covalent bonds form when two atoms share electrons.
Metallic bonds result from the attraction between positively charged metal ions and delocalized electrons.

Matter can exist in three states: solid, liquid, and gas.
Solids have a definite shape and volume because their particles are tightly packed.
Liquids have a definite volume but take the shape of their container because particles are close but can move past each other.
Gases have no definite shape or volume because their particles are far apart and move freely.

Chemical reactions involve reactants, which are the substances that undergo change, and products, which are the new substances formed.
There are five main types of chemical reactions: synthesis, decomposition, single replacement, double replacement, and combustion.

The mole is a unit of measurement for the amount of substance.
One mole contains Avogadro's number of particles, which is 6.022 x 10²³ particles.
Molar mass is the mass of one mole of a substance and is typically expressed in grams per mole.

Acids donate protons (H⁺ ions) in solution and turn blue litmus paper red.
Bases accept protons or donate hydroxide ions (OH⁻) in solution and turn red litmus paper blue.
The pH scale ranges from 0 to 14 and measures the acidity or basicity of a solution.
A pH of 7 is neutral.

Exothermic reactions release heat, making the products have lower energy than the reactants.
Endothermic reactions absorb heat, making the products have higher energy than the reactants.
Activation energy is the minimum amount of energy required for a reaction to occur.

Elements in the periodic table are organized into groups (vertical columns) and periods (horizontal rows).
Elements within the same group share similar chemical properties.
Elements within the same period have the same number of electron shells.
Elements can also be broadly classified as metals, nonmetals, or metalloids based on their physical and chemical properties.

The atomic theory states that all matter is composed of atoms and that atoms of a given element are identical.
The kinetic molecular theory explains the behavior of gases in terms of particle motion.

When working in a laboratory, always wear safety goggles and gloves.
It is important to know the location of safety equipment, such as eye washes and fire extinguishers.
Chemicals should be properly labeled and stored to prevent accidents.