Chemistry: Electron Configuration and Periodic Trends

Electron Configuration

• Electron configuration: the arrangement of electrons in an atom's energy levels
• Aufbau principle: electrons occupy the lowest available energy levels
• Hund's rule: electrons occupy degenerate orbitals singly before filling them in pairs
• Pauli's exclusion principle: no two electrons can have the same set of quantum numbers

Periodic Trends

• Periodic table organization: elements arranged by atomic number (Z) and recurring chemical properties
• Periodic trends:
  • Atomic radius: decreases from left to right across a period, increases down a group
  • Electronegativity: increases from left to right across a period, decreases down a group
  • Ionization energy: increases from left to right across a period, decreases down a group
  • Electron affinity: increases from left to right across a period, decreases down a group

Ionic Bonds

• Ionic bond: electrostatic attraction between oppositely charged ions
• Formation:
  • Metal loses electron(s) to form a cation
  • Nonmetal gains electron(s) to form an anion
• Characteristics:
  • Strong electrostatic attraction between ions
  • High melting and boiling points
  • Often soluble in water

Wave Properties

• Wave-particle duality: particles (e.g., electrons) exhibit wave-like behavior
• Wave characteristics:
  • Wavelength (λ): distance between consecutive peaks or troughs
  • Frequency (ν): number of oscillations per second
  • Speed (c): wavelength × frequency
• Wave behavior:
  • Diffraction: bending of waves around obstacles
  • Interference: superposition of waves

Newton's Laws

• First law (inertia): an object at rest remains at rest, an object in motion remains in motion, unless acted upon by an external force
• Second law (force and acceleration): F = ma (force equals mass times acceleration)
• Third law (action and reaction): every action has an equal and opposite reaction

Unit Conversions

• Length:
  • Meter (m) → centimeter (cm): 1 m = 100 cm
  • Meter (m) → millimeter (mm): 1 m = 1000 mm
• Volume:
  • Liter (L) → milliliter (mL): 1 L = 1000 mL
• Mass:
  • Gram (g) → milligram (mg): 1 g = 1000 mg

Atomic Structure

• Atomic model:
  • Nucleus (protons and neutrons) surrounded by electrons
  • Electron cloud: region where electrons are likely to be found
• Subatomic particles:
  • Protons: positively charged, found in nucleus
  • Neutrons: no charge, found in nucleus
  • Electrons: negatively charged, found in electron cloud

Covalent Bonds

• Covalent bond: sharing of electrons between atoms
• Formation:
  • Atoms share one or more pairs of electrons
• Characteristics:
  • Typically between nonmetals
  • Lower melting and boiling points compared to ionic compounds
  • Often insoluble in water

Metallic Bonds

• Metallic bond: delocalization of electrons in a "sea of electrons"
• Formation:
  • Atoms lose electrons to form a "sea of electrons"
• Characteristics:
  • High electrical conductivity
  • Malleability and ductility
  • High thermal conductivity

Electron Configuration

• Electron configuration is the arrangement of electrons in an atom's energy levels
• Aufbau principle: electrons occupy the lowest available energy levels
• Hund's rule: electrons occupy degenerate orbitals singly before filling them in pairs
• Pauli's exclusion principle: no two electrons can have the same set of quantum numbers

Periodic Trends

• The periodic table is organized by atomic number (Z) and recurring chemical properties
• Periodic trends include:
  • Atomic radius: decreases from left to right across a period, increases down a group
  • Electronegativity: increases from left to right across a period, decreases down a group
  • Ionization energy: increases from left to right across a period, decreases down a group
  • Electron affinity: increases from left to right across a period, decreases down a group

Ionic Bonds

• Ionic bonds are electrostatic attractions between oppositely charged ions
• Formation:
  • Metal loses electron(s) to form a cation
  • Nonmetal gains electron(s) to form an anion
• Characteristics:
  • Strong electrostatic attraction between ions
  • High melting and boiling points
  • Often soluble in water

Wave Properties

• Wave-particle duality: particles (e.g., electrons) exhibit wave-like behavior
• Wave characteristics:
  • Wavelength (λ): distance between consecutive peaks or troughs
  • Frequency (ν): number of oscillations per second
  • Speed (c): wavelength × frequency
• Wave behavior:
  • Diffraction: bending of waves around obstacles
  • Interference: superposition of waves

Newton's Laws

• First law (inertia): an object at rest remains at rest, an object in motion remains in motion, unless acted upon by an external force
• Second law (force and acceleration): F = ma (force equals mass times acceleration)
• Third law (action and reaction): every action has an equal and opposite reaction

Unit Conversions

• Length:
  • 1 meter (m) = 100 centimeters (cm)
  • 1 meter (m) = 1000 millimeters (mm)
• Volume:
  • 1 liter (L) = 1000 milliliters (mL)
• Mass:
  • 1 gram (g) = 1000 milligrams (mg)

Atomic Structure

• Atomic model:
  • Nucleus (protons and neutrons) surrounded by electrons
  • Electron cloud: region where electrons are likely to be found
• Subatomic particles:
  • Protons: positively charged, found in nucleus
  • Neutrons: no charge, found in nucleus
  • Electrons: negatively charged, found in electron cloud

Covalent Bonds

• Covalent bonds: sharing of electrons between atoms
• Formation:
  • Atoms share one or more pairs of electrons
• Characteristics:
  • Typically between nonmetals
  • Lower melting and boiling points compared to ionic compounds
  • Often insoluble in water

Metallic Bonds

• Metallic bonds: delocalization of electrons in a "sea of electrons"
• Formation:
  • Atoms lose electrons to form a "sea of electrons"
• Characteristics:
  • High electrical conductivity
  • Malleability and ductility
  • High thermal conductivity

Electron Configuration

• Electron configuration is the arrangement of electrons in an atom's orbitals
• Aufbau principle states that electrons occupy the lowest available energy levels
• Pauli's exclusion principle states that no two electrons in an atom can have the same set of quantum numbers
• Hund's rule states that electrons occupy degenerate orbitals singly before pairing up
• Electron configuration notation is written in the format 1s2 2s2 2p6, etc.

Periodic Trends

• Atomic radius decreases across a period and increases down a group
• Electronegativity increases across a period and decreases down a group
• Ionization energy increases across a period and decreases down a group
• Metallic character increases down a group and decreases across a period

Ionic Bonds

• Ionic bonds are formed through the electrostatic attraction between oppositely charged ions
• Ionic bonds are typically formed between metals and nonmetals
• Characteristics of ionic bonds include high melting and boiling points, solids at room temperature, and the ability to conduct electricity when dissolved in water

Wave Properties

• Wave-particle duality states that particles can exhibit wave-like behavior
• Wave characteristics include wavelength (λ), frequency (f), speed (c), and amplitude (A)
• The superposition principle states that waves can combine to form a new wave
• Interference patterns can be constructive or destructive

Newton's Laws

• Newton's first law states that an object at rest remains at rest, and an object in motion remains in motion
• Newton's second law states that force (F) is equal to mass (m) multiplied by acceleration (a)
• Newton's third law states that every action has an equal and opposite reaction

Atomic Structure

• Atomic structure refers to the composition of an atom
• Subatomic particles include protons (positively charged, found in nucleus), neutrons (no charge, found in nucleus), and electrons (negatively charged, found in orbitals)
• The atomic nucleus is composed of protons and neutrons in the center of the atom

Covalent Bonds

• Covalent bonds are formed through the sharing of electrons between atoms
• Covalent bonds are typically formed between nonmetals
• Characteristics of covalent bonds include low melting and boiling points, and the ability to be solids, liquids, or gases at room temperature
• Covalent bonds are poor conductors of electricity

Metallic Bonds

• Metallic bonds are formed through the delocalization of electrons in a metal lattice
• Metallic bonds are typically formed between metals
• Characteristics of metallic bonds include high melting and boiling points, good conductivity, and the ability to be malleable and ductile