Year 11 Semester 1 exams

• The properties of elements change gradually with their atomic number, and these changes occur periodically
• Periodic table


  • Organizes elements based on their repeating properties
  • Arranges elements in rows by increasing atomic number
  • Arranges elements in columns by similar chemical properties
  • Rows are called periods
  • Columns are called groups
  • Helps predict an element's properties and the compounds it might form
• In 1869, Dmitri Mendeleev made a significant early attempt at organizing the periodic table
• Mendeleev's periodic table


  • Based on increasing molar mass
  • Considered the precursor to the modern table
  • Mendeleev successfully predicted the existence and properties of gallium, scandium, and germanium using his periodic table
• Electron configurations


  Describe where electrons are located around the nucleus of an atom
• Halogens


  • Group 17
  • Quite reactive non-metal elements
  • Produce ionic compounds with metals where the halogens form -1 ions
• Noble gases


  • Group 18
  • Non-metal gases with very low chemical reactivity
  • Only a handful of examples where noble gases form compounds
• Alkali metals


  • Group 1
  • Soft low melting point metals
  • React vigorously with water and acids to produce hydrogen gas
  • Alkali metal compounds are all ionic with the elements always forming +1 ions
• Alkali earth metals


  • Group 2
  • Metals that react strongly with acids producing hydrogen gas
  • React with water (except Be) producing a metal hydroxide and hydrogen gas
  • Their compounds are ionic (except Be) with the metals always forming +2 ions
• Atomic radius


  • The total distance from the nucleus of an atom to the outermost orbital of its electron
  • Decreases as you move from left to right across a period (due to increasing nuclear charge)
  • Increases as you move down a group (due to the increasing number of electron shells)
• Ionisation energy


  • The amount of energy required to remove an electron from an isolated atom or molecule
  • Increases from left to right within a period (due to valence shell stability)
  • Decreases from top to bottom within a group (due to electron shielding)
• Electronegativity


  • The electron attracting power of an atom, excluding noble gases
  • Generally increases across a period (left-> right)
  • Increases up a group
• Fluorine is the most electronegative element in the periodic table
• Non-metal elements


  • Typically have a covalent molecular structure
  • Their formula indicates the number of atoms in one molecule of the element
• Substances with a covalent molecular structure are made up of molecules, which are groups of two or more atoms bonded together by covalent bonds
• Substances containing only non-metal elements form covalent molecular substances, with exceptions including covalent network materials like silicon carbide, silicon dioxide, carbon (diamond and graphite), and silicon
• Systematic naming


  • Uses prefixes such as mono = 1, di = 2, tri = 3, tetra = 4, Penta = 5, hexa = 6 to indicate the number of each atom in one molecule of the compound
  • For oxygen, mon, di, tri, tetr, pent and hex are used
  • Mono is never used for the first named element
• Ionic compounds


  • Form from metal and non-metal elements, creating positively and negatively charged ions
  • Ions can be monatomic (e.g., Na⁺, Br⁻) or polyatomic (e.g., OH⁻, NH₄⁺)
  • Result from atoms losing or gaining electrons, becoming positively or negatively charged
  • Metals lose electrons to form positive ions, while non-metals gain electrons to form negative ions
• Writing an ionic formula

  1. Ensure the compound is ionic, that is it contains both metal and non-metal elements in its formula

  2. Write the formula for the positive ion first followed by the negative ion

  3. Determine the least number of positive and negative ions that gives a neutral combination

  4. Write these numbers as subscripts to the ions

  5. Remove the ion charges and do not alter any subscripts already present in the ion formula

  6. Use brackets if a subscript is needed for a polyatomic ion
• Physical properties of substances

  • Encompass characteristics such as melting point, malleability, and conductivity of heat or electricity
  • Indicate four distinct classes of substances, each with its unique combination of these traits
• Metallic bonding


  • Atoms release valence electrons to achieve noble gas configuration, forming positive metal ions and free electrons
  • Positive metal ions form a fixed lattice structure
  • Released valence electrons move randomly among the metal ion lattices, forming a "sea" of mobile electrons
  • Metallic bonding arises from the strong electrostatic attraction between stationary metal ions and the mobile sea of electrons
• Ionic bonding


  • Forms when metallic elements (or NH₄⁺ ions) combine with non-metallic elements
  • Metal element loses all its valence electrons to achieve a noble gas electron configuration, forming a positive ion
  • Transferred electrons are gained by the non-metal element, forming a negative ion also with a noble gas electron configuration
  • Positive and negative ions create a 3D ionic lattice, bonding through strong electrostatic attraction between neighbouring ions
• Covalent bonding


  • Forms when non-metal elements bond together, usually found on the upper right side of the periodic table
  • Atoms share valence electrons to reach a noble gas electron configuration
  • Covalent bonds have directionality, with electrons shared along a specific axis between two atoms
• Covalent molecular bonding


  • In covalent molecular substances, atoms bond together in small clusters called molecules
  • Strong covalent bonds within these molecules are called intramolecular forces
  • Weak forces like van der Waals forces create slight attraction between molecules, known as intermolecular forces
• Covalent network structure


  • Unlike covalent molecular materials, the strong covalent bonding extends continuously throughout the substance
  • In diamond, each carbon atom is bonded to four neighbouring carbon atoms in a three-dimensional arrangement called a tetrahedron
  • In graphite, each carbon atom is covalently bonded to three neighbouring atoms to form flat two-dimensional sheets, called graphene, with weak bonds between the layers
  • Graphite has one valence electron from each carbon atom remaining delocalised and able to move freely between the graphene layers
• Fullerenes


  • Allotropic form of carbon
  • The molecule known as a buckminsterfullerene, C60, or 'buckyball' consists of 60 carbon atoms covalently bonded into a cage structure
  • Similar cage structures have been identified with 70, 80 and more carbon atoms
  • C60 and other fullerenes occur naturally in small concentrations in soot
• Carbon nanotubes (CNTs)


  • Tube structures like a rolled-up graphene sheet
  • Carbon atoms along the cylinder's length form interlocking hexagonal arrangements
  • Can be produced with multiple walls, called multi-walled nanotubes (MWNTs)
  • Each atom in a single CNT is bonded strongly to its neighbors, making CNTs remarkably strong and flexible
  • CNTs can act as semiconductors or excellent conductors depending on their diameter and symmetry
• Nanoparticles


  • Tiny particles ranging from 1 to 100 nanometres in size
  • Nanotechnology studies these particles, their structures, production, and potential uses
  • Often exhibit unique properties due to their small size, including quantum effects
• Carbon nanotubes (CNTs) show distinct electrical properties compared to their bulk material, with potential in creating nano-sized transistors and diodes
• Electrolysis


  A technique used to split compounds into their elements by passing an electric current through an electrolyte
• For electrolysis to work, the ions in the electrolyte have to be free to move around</b>
• Insoluble compounds


  Need to be melted to make them a molten liquid for electrolysis
• Soluble compounds


  Can be dissolved in water to make the electrolyte
• Electrolyte


  A substance that when dissolved in water will dissociate into positively charged and negatively charged ions, which have the ability to conduct electricity in solution
• Nonelectrolyte


  A substance that will not dissociate into ions when dissolved in water and therefore cannot conduct electricity
• Strong electrolyte


  A substance that completely dissociates in solution and will conduct electricity very well
• Weak electrolyte


  A substance that only partially ionizes in solution, meaning some particles dissociate and some do not, and will still conduct electricity, but not as well as a strong electrolyte
• Ionic electrolytes


  • Ionic compounds that will dissociate in aqueous solution to give individual cations and anions
  • Dissociation occurs due to ion-dipole interactions with water molecules and greater disorder of solution over crystallized ionic solid
• Covalent electrolytes


  • Covalent species undergo chemical reaction with solvent molecules to form charged products
  • Strong acids and bases that either donate or remove a proton from water
• Solubility rules help us predict whether or not a salt is soluble in water