Basic Concepts of Chemistry

Atoms: Basic unit of matter, composed of protons, neutrons, and electrons.
Molecules: Two or more atoms bonded together.
Elements: Pure substances made of only one type of atom; organized in the Periodic Table.
Compounds: Substances formed when two or more different elements are chemically bonded.

Nucleus: Center of an atom containing protons (positive charge) and neutrons (no charge).
Electrons: Negatively charged particles orbiting the nucleus in energy levels.
Atomic Number: Number of protons in an atom; defines the element.
Mass Number: Total number of protons and neutrons in an atom's nucleus.

Ionic Bonds: Formed when electrons are transferred from one atom to another; results in charged ions.
Covalent Bonds: Formed when atoms share electrons; can be single, double, or triple bonds.
Metallic Bonds: Involves the pooling of electrons in metals, allowing for conductivity and malleability.

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

Reactants: Substances that undergo a change in a chemical reaction.
Products: Substances formed as a result of a chemical reaction.
Types of Reactions:
- Synthesis: Two or more substances combine to form a new compound.
- Decomposition: A single compound breaks down into simpler products.
- Single Replacement: One element replaces another in a compound.
- Double Replacement: Exchange of ions between two compounds.
- Combustion: A substance reacts with oxygen, releasing energy in the form of light and heat.

Solvent: Substance that dissolves a solute; usually present in greater amount.
Solute: Substance that is dissolved.
Concentration: Amount of solute in a given volume of solvent; can be expressed in molarity (moles per liter).

Acids: Substances that donate protons (H⁺) in solution; characterized by a sour taste, pH less than 7.
Bases: Substances that accept protons or donate hydroxide ions (OH⁻); characterized by a bitter taste, pH greater than 7.
pH Scale: Ranges from 0 to 14; measures acidity (0-6) and basicity (8-14), with 7 being neutral.

Groups: Vertical columns; elements share similar properties (e.g., alkali metals, halogens).
Periods: Horizontal rows; properties change progressively from left to right.
Electronegativity: Tendency of an atom to attract electrons; increases across a period and decreases down a group.

Law of Conservation of Mass: Mass is neither created nor destroyed in a chemical reaction.
Avogadro's Law: Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.
Mole Concept: 1 mole = 6.022 x 10²³ entities (Avogadro's number); used for counting particles in chemistry.

Matter is made up of tiny particles called atoms
Atoms combine to form molecules
Elements are pure substances made of one type of atom and are organized on the Periodic Table
Compounds are formed when two or more different elements chemically bond

The nucleus is located at the center of an atom and contains protons and neutrons
Protons have a positive charge, neutrons have no charge
Electrons are negatively charged particles that orbit the nucleus in energy levels
The atomic number of an atom is defined by the number of protons
The mass number of an atom is the total count of protons and neutrons in its nucleus

When electrons are transferred between atoms it's called an ionic bond
Ionic bonds result in charged ions
When atoms share electrons it's called a covalent bond
Covalent bonds can be single, double, or triple bonds depending on the numbers of electrons shared
Metallic bonds occur when electrons are shared across a metal, which contributes to its conductivity and malleability

Solids have a rigid shape and fixed volume due to tightly packed molecules
Liquids maintain a fixed volume but take the shape of their container because molecules are closely packed but move around
Gases don't have a fixed shape or volume because molecules are spaced far apart and move freely

Reactants are the substances that change during a reaction
Products are the substances formed as a result of a chemical reaction
Synthesis reactions occur when two or more substances combine to make a new compound
Decomposition reactions occur when a single compound breaks down into simpler products
Single replacement reactions occur when one element replaces another in a compound
Double replacement reactions occur when the ions from two compounds exchange places
Combustion reactions occur when a substance reacts with oxygen, releasing energy in the form of light and heat

A solvent dissolves a solute
The solvent is usually present in a greater amount
Concentration describes the amount of solute in a given volume of solvent
Molarity is a common unit of concentration that expresses the number of moles of solute per liter of solution

Acids donate protons, or H⁺, in a solution
Acids have a sour taste and a pH less than 7
Bases accept protons and donate hydroxide ions, or OH⁻
Bases have a bitter taste and a pH greater than 7
The pH scale ranges from 0 to 14, with 0-6 indicating acidity, 8-14 indicating basicity, and 7 being neutral

The periodic table organizes elements based on their properties
Elements with similar properties are found in the same vertical column, which are called groups
Elements in the same horizontal row, or period, have properties that change progressively from left to right
The periodic table can be used to predict trends in electronegativity, a measure of an atom's attraction to electrons, which increases across a period and decreases down a group

The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction
Avogadro's law states that equal volumes of gases at the same temperature and pressure contain an equal number of molecules
The mole is a unit used for counting particles in chemistry, with 1 mole equaling 6.022 x 10²³ entities, also known as Avogadro's number