PSC

• Matter is any substance that has mass and occupies space.  It is made up of different particles.  The properties of the particles determine the characteristics of matter and how it reacts.
• Pure substances vs Mixtures: A pure substance has definite physical and chemical properties, and a definite composition.

  Element: a material that consists of one kind of atom only. (see formal definition later)

  Examples: 

  Compound: a substance that is formed when two or more elements bond chemically in a fixed ratio. Examples: H2O,           

  Mixtures: a combination of two or more substances that have different physical properties and that are not bonded.
• Chemical Properties: These are the ability of a substance to undergo a change into another form through a chemical reaction with other substances. Chemical reactions produce new substances with different properties from those of the reactants. For example, burning wood produces ash, carbon dioxide gas, water vapor, heat, light, and sound.
• 1. Properties of matter

  • Strength: how much force it can withstand before changing shape
  • Thermal conductivity: how well a material conducts heat
  • Electrical conductivity: how well a material conducts electricity
  • Brittleness, Malleability and Ductility: how easily a material can be shaped without breaking
  • Magnetism
  • Melting point and Boiling point
• 1. STATES OF MATTER

  Matter is found in either the solid, liquid or gaseous phase depending on the temperature and pressure
• Metalloids are the elements with both metal and non-metal properties and are found on the boundary between them on the PT.
• 1. THE KINETIC MOLECULAR THEORY

  States that:

  • All matter consists of constantly moving particles.
  • The particles do not all have the same amount of kinetic energy and so an average is referred to. 
  • Temperature (in kelvin = K) is a measure of the average amount of kinetic energy of the particles.
  • The particles can exert forces on one another.

  The random motion of the particles is called Brownian motion.  This can be illustrated by diffusion. 
• The temperature of a substance does not change while it is undergoing a phase change.  This is because the energy added/released is not changing the kinetic energy (movement) of the particles but the attractive forces between the particles.

  Temperature is a measure of average kinetic energy.
• An element has been described as a substance that cannot be

  split into anything simpler. The smallest unit that makes up an

  element is an atom. ("atomos" - "indivisible").

  Atoms remain relatively unchanged in chemical reactions but

  may be split in nuclear reactions.
• The nucleus of an atom remains unchanged in chemical

  reactions but electrons are easily lost or gained. An atom with

  an uneven charge is called an ion.
• An atom that has lost an electron(s) is positively charged and

  is called a cation.

  An atom that has gained an electron(s) is negatively charged

  and is called an anion.
• An element is a substance where all the atoms have the same

  atomic number (or: same number of protons)
• Isotopes are atoms of the same element that have different

  masses (different numbers of neutrons).
• The relative atomic mass of an atom is the average mass of an

  atom of that element compared to the mass of one twelfth of a

  carbon-12 atom.
• 2.ELECTRONIC STRUCTURE

  In Bohr's model of the atom:

  the electrons spin around the nucleus in "orbits".

  the further the orbit from the nucleus, the greater the amount

  of energy of the electrons

  • an electron do not lose energy while it moves in its own

  orbit, but gives off energy if it falls to an orbit closer to the

  nucleus.
• An energy-level is a region around the nucleus where the

  probability of finding an

  electron of particular energy is greatest.
• Ionisation energy is the energy needed to remove an electron

  from an atom.

  The First Ionisation Energy is the energy needed to remove the

  first/outermost electron of an atom.

  The first ionisation energy will be the lowest as it is easier to

  remove the electron that is furthest from the nucleus.

  The amount of energy needed will increase as more electrons

  are removed.
• An orbital is a region of probability within an energy-level

  where an electron can be found.
• Each orbital can hold a maximum of two electrons, provided

  they have opposite spin – Pauli's Exclusion Principle.
• s-orbitals:

  have the lowest energy

  each energy-level has one s-orbital.

  p-orbitals:

  have slightly higher energy than s-orbitals

  from level 2 upwards

  • each energy-level has three p-orbitals.

  Five d-orbitals occur from level 3 upwards and seven f-orbitals

  occur in each energy-level from four upwards.
• Rules of electron configuration:

  1. Energy-levels are filled from the bottom up

  2. s-orbitals are filled first, then p-, d- and f-orbitals

  3. Each orbital can contain a maximum of two electrons

  provided they have opposite spin. This is known as

  Pauli's Exclusion Principle.

  4. Each p-orbital must first contain one electron before sharing

  takes place. This is known as Hund's rule.