Chemistry: Atomic Structure and Periodic Table

Atomic Structure

• Atoms are the smallest units of an element, composed of protons, neutrons, and electrons.
• Protons are positively charged, found in the nucleus, and determine the element.
• Neutrons are neutrally charged, also in the nucleus, and contribute to atomic mass.
• Electrons are negatively charged, orbiting the nucleus in energy levels (shells).
• Electron configuration describes the arrangement of electrons in energy levels.
• Atomic number (Z) is the number of protons.
• Mass number (A) is the sum of protons and neutrons.
• Isotopes are variations of an element with the same number of protons but different numbers of neutrons.

The Periodic Table

• The periodic table organizes elements by increasing atomic number and similar properties.
• Groups (vertical columns) contain elements with similar chemical properties due to similar outer electron configurations.
• Periods (horizontal rows) show gradual changes in properties, reflecting the number of electron shells.
• Elements are classified as metals, nonmetals, or metalloids.
• Alkali metals (Group 1) are highly reactive, especially with water.
• Halogens (Group 17) are reactive nonmetals.
• Noble gases (Group 18) are inert with complete electron shells.

Elements, Compounds, and Mixtures

• Elements are pure substances of one type of atom.
• Compounds are formed by chemically bonded elements.
• Mixtures combine substances without chemical bonds, physically separable.

Types of Bonds

• Ionic bonds involve electron transfer, forming positive and negative ions.
• Covalent bonds involve electron sharing.

Naming Compounds

• Ionic compounds combine cation (positive) and anion (negative) names.
• Covalent compounds use prefixes to indicate the number of atoms.

Chemical Equations

• Word equations use names, symbol equations use formulas.
• Balancing equations ensures equal atoms on both sides.

Nanoscience

• Nanoscience studies materials at the nanoscale (1-100 nanometers).
• Nanoparticles have unique properties due to large surface area.
• Applications include medicine, electronics, and materials science.

Magnets and Magnetic Fields

• Magnets produce magnetic fields with field lines running from north to south.
• Like magnetic poles repel, unlike poles attract.

Electromagnets

• Electromagnets use electric current to create a magnetic field.
• They are formed by a coil of wire (solenoid) often with an iron core.
• Uses include electric motors, generators, and magnetic cranes.

Static Electricity

• Static electricity is the buildup of electric charge.
• Discharge occurs when objects come into contact.
• Applications include lightning, photocopiers, and electrostatic precipitators.

Electricity: Circuits and Components

• Circuits are complete paths for electric current.
• Components include resistors (limit current), capacitors (store energy), switches, batteries, and bulbs.

Electric Current, Voltage, and Resistance

• Current (I) is the flow of charge (measured in amperes).
• Voltage (V) is the potential difference (measured in volts).
• Resistance (R) is the opposition to current (measured in ohms).
• Ohm's Law: V = IR