Properties and Structure of Matter

• An atom is composed of three subatomic particles: Protons, Neutrons, and Electrons
• Protons and Neutrons are found in the nucleus of the atom, while Electrons are located in orbits around the nucleus
• Protons and Neutrons have around the same mass, approximately 1 atomic mass unit (1u), while Electrons are much lighter at around 0.0005u
• Protons have a positive +1 charge, Neutrons are neutral, and Electrons have a negative -1 charge
• Particle theory states that all matter is made from very small particles that are constantly in motion
• In solids, particles are packed closely together with less heat and kinetic energy, leading to fixed shapes and volume
• Liquids have more heat and kinetic energy, allowing particles to move more freely, resulting in a fixed volume but no fixed shape
• Gases have even more heat and kinetic energy, causing particles to move freely with no fixed shape or volume
• Elements and Compounds are pure substances with fixed compositions and properties, while Mixtures are impure substances with variable compositions and properties
• Elements are made of one type of atom, with fixed properties defined by the number of protons in the nucleus
• Compounds consist of different types of atoms bonded together in fixed ratios, with properties distinct from the elements that make them up
• Mixtures are made of two or more substances mixed together without chemical bonding, leading to variable properties
• Solutions are homogeneous mixtures with particles evenly dissolved, Colloids have particles that do not settle out, and Suspensions have particles that settle out by gravity
• Density is the mass per unit volume of a substance, generally measured in grams per mL (g/mL)
• Chemical properties of a substance can only be determined through chemical reactions, such as reactivity, pH, and toxicity
• Separation techniques based on physical properties include Magnetic separation, Evaporation, Sieving, Filtration, Distillation, and Separating funnel
• Gravimetric analysis is used to analyze the percentage composition of a mixture
• Investigate the basic structure of stable and unstable isotopes by examining
• Investigate the basic structure of stable and unstable isotopes by examining:

  • Position in the periodic table
  • Distribution of electrons, protons, and neutrons in the atom
  • Representation of the symbol, atomic number, and mass number (nucleon number)
• Model the atom’s discrete energy levels, including electronic configuration and spdf notation
• Calculate the relative atomic mass from isotopic composition
• Investigate energy levels in atoms and ions through:

  • Collecting primary data from a flame test using different ionic solutions of metals
  • Examining spectral evidence for the Bohr model and introducing the Schrödinger model
• Investigate the properties of unstable isotopes using natural and human-made radioisotopes as examples, including:

  • Types of radiation
  • Types of balanced nuclear reactions
• The periodic table is arranged so that elements with similar properties are close to each other

  • Columns are called groups (1 to 18)
  • Rows are called periods (1 to 7)
  • Special group names: Alkaline metals, Alkaline earth metals, Transition metals, Halogens, Noble Gases
• Metals are solids at room temperature, shiny, good conductors of heat and electricity, malleable, and ductile

  • Non-metals have opposite properties to metals
  • Metalloids have properties between metals and non-metals
• Atoms are arranged by atomic number (number of protons)

  • Mass number = protons + neutrons
  • Atomic weight is given on the periodic table
  • Proton = Atomic number
  • Electron = Atomic number
  • Neutral = Mass number - atomic number
• Isotopes are atoms of an element with different numbers of neutrons

  • Atomic weight is determined by the relative abundance of each isotope
  • Isotopes of the same element have similar properties
  • Some isotopes can become radioactive
• Nucleus becomes unstable when too large or ratio of protons to neutrons is skewed

  • Unstable isotopes emit radiation to decay into a more stable form
  • Types of nuclear radiation: alpha, beta, gamma
• Alpha radiation is a 2+ positive particle consisting of two protons and two neutrons

  • Beta radiation is a -1 negative particle consisting of one electron
  • Gamma radiation is pure energy in the electromagnetic spectrum
• Half-life is the time for half of the mass of a radioisotope to decay

  • Man-made isotopes are atoms larger than uranium
  • Penetrating power: Gamma > Beta > Alpha
  • Ionising potential: Alpha > Beta > Gamma
• Electron configuration: Electrons in shells around the nucleus

  • Valence shell contains valence electrons, important for chemical reactions
  • Octet rule: Atoms seek 8 valence electrons for stability
• Sublevels s, p, d, f have different number of orbitals and electrons they can hold

  • Each energy level contains different sublevels
• An orbital is a region where there is a 90% chance of finding an electron

  • Shapes of sublevels: "s" is a sphere, "p" is 3 dumbbell-shaped orbitals
• "p" sublevel:

  • Made from 3 identical dumbbell-shaped orbitals
  • Each shape is on its own axis (x, y, z) and they are 90 degrees from one another
• "d" sublevel:

  • Has 5 different orbitals
• "f" sublevel:

  • Has 7 different orbitals
• Electrons fill up shells based on the energy required

  • 4s gets filled before 3d because it requires less energy
• Orbital notation:

  • A way to show electrons in s, p, d, f orbitals
  • Example: Argon's electron configuration is 2, 8, 8
  • Written as orbital notation: 1s 2 2s 2 2p 6 3s 2 3p 6
  • Each sublevel can only hold a specific number of electrons
• Potassium's electron configuration:

  • 2, 8, 8, 1
  • Orbital notation: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1
  • Can be simplified as [Ar]4s 1
• Hund's rule:

  • States that every orbital is singly occupied before any orbital is doubly occupied
  • Example: Nitrogen 1s 2 2s 2 2p 3 Oxygen 1s 2 2s 2 2p 4