Atomic structure and the periodic table

• What are some limitations of the particle model for state matter?


  -does not consider intermolecular forces that exist between particles

  -assumes particles to be small, solid and unelastic

  -doesn't consider sizes, shapes and spaces
• What is an atom?


  -An atom is the smallest part of an element that can exist!
• What is an element?


  An element is a substance of only one type of atom!
• How are the elements listed and approximately how many are there?


  They are listed in the periodic table, there are approximatly 100!
• What are the two groups in which elements are organised in based on their properties?

  metals and non-metals
• What is a compound?


  A substance formed by two or more elements chemically bonded together which can be represented by formulae!
• Do compounds have the same properties as their constituent elements?


  No, they have different properties!
• What is a mixture? And does it have the same chemical properties as its consituent materials?


  A mizture consists of two or more elements or compounds NOT chemically bonded together, it does have the same chemical properties!
• What are the five methods through which mixtures can be seperated?


  Filtration, crystallisation, simple distillation, fractional distillation, chromatography ; they do NOT involve chemical reactions!
• Describe and explain simple distillation!


  Simple distillation is used to separate a liquid from a solution - the liquid boils off an condenses in the condensing tube, the thermometer will read the boiling point of the pure liquid, contrary to evaporation, we get to keep the liquid!
• Describe and explain crystallisation!


  Crystallisation is similar to evaporation, however in crystallisation we only remove some of the solvent by evaporation then form a saturated solution (the one where no more solid can be dissolved), then we cool down the solution, as we do so the solid starts to crystalise as it becomes less soluble at lower temperatures, the crystals can be collected and seperated from the solvent via filtration!
• Describe and explain evaporation!


  Evaporation is a technique for separation of a solid dissolved in a solvent from a solvent (eg salt from H20) - the solution is heated until all the solvent evaporates and the solids remain in the vessel!
• Describe and explain fractional distillation!

  Fractional distillation is a technique for separation of a mixture of liquids working when liquids have DIFFERENT boiling points! - the apparatus is similar to the one of simple distillation apparatus with the additional fractionating column placed on top of the heated flask - the fractionating column contains glass beads, helping to sperate the compounds, in industry mixtures are repeatedly condensed and vapourised as the column ins hot and the bottom and cold at the top, the liquids will condense at different heights in the column!
• Describe and explain filtration!

  Filtration is used to separate an insoluble solid that is supsneded in a liquid - the insoluble solid (called a residue) gets caught in the filter paper - because the particles are too big to fit through the holes in the paper - the filtrate is the substance that comes through the filter paper! - apparatus = filter paper + funnel!
• Describe and explain chromatography!


  Chromatography is used to separate a mixture of substances dissolved in a solvent - in paper chromatography we place a piece of paper with a spot containing a mixture in a beaker with some solvent, the bottom of the paper has to be in contact with the solvent, the solvent level will slowly start to rise, thus separating the spot (mixture) into few spots (components)
• What is a separating funnel?


  A separatory funnel is n apparatus for separating immiscible liquids - two immiscible liquids of different densities will from two distinct layers in the separatory funnel - we can run off the bottom layer (liquid with a greater density) to a separate vessel!
• Define the plum-pudding model


  The atom is a ball of positive charge with negative electrons embedded inside it!
• Describe the Bohr/nuclear model and how it came about!


  The nuclear model suggests that electrons robit the nucleus at a specific distances (shells) - it came about from the alpha scattering experiments!
• After the plum pudding and Bohr model, a discovery was made regarding smaller, positive particles in the nucleus of an atom, what are they called?


  Protons!
• What did the work of James Chadwick provide evidence for?


  The existence of neutrons in the nucleus!
• Describe the structure of an atom!

  The atom has a small central nucleus (made up of protons and neutrons) around which there are electrons!
• State the relative masses and relative charges of the proton, neutron and electron!


  MASSES: [proton = 1] [neutron = 1] [electron = very small]

  CHARGES: [proton = 1] [neutron = 0] [electron = -1]
• Explain why atoms are electrically neutral


  Because they have the same number of electrons and protons! (think PEN!)
• What is the radius of an atom?


  0.1 nm
• What is the radius of a nucleus and what is that compared to that of the atom?


  RADIUS OF NUCLEUS : 1 X 10-14

  IN COMPARISON : 1/10000
• What is the name given to the number of protons in the nucleus?

  Atomic number
• Atoms of the same element have the same number of which particle in the nucleus?


  Protons
• Where is the majority of mass in an atom?

  Nucleus
• What is the mass number?


  The total number of protons and neutrons!
• How do you calculate the number of neutrons using mass number and atomic number?


  Subtract atomic number from mass number.
• What is an isotope? And do isotopes of a certain element have the same chemical properties?


  Isotopes are atoms of the same element (having the same proton number) that have a different number of neutrons!

  They have the same chemical properties as they have the same electronic structure!
• What is the relative atomic mass?


  The average mass value which takes the mass and abundance of isotopes of an element into account, on a scale where the mass of 12C is 12!
• Give the electronic configurations of He(2), Be(4), F(9), Na(11) and Ca(20)


  He = 2

  Fe = 2,2

  F = 2,7

  Na = 2,8,1

  Ca = 2,8,8,2
• What are ions?


  Ions are charged particles, they are formed when atoms lose electrons (positive ions) or gain (negative ions) electrons!

  EG: sodium positive ion Na+ has an electronic configuration of 2,9, an atom of sodium has lost on electron!
• What is formed when a metal reacts with a non-metal?


  Ionic compound (made of positive and negative ions)
• What is formed when a non-metal reacts with a non-metal?


  A molecular compound containing covalently bonded atoms! - atoms share electrons, as opposed to transferring electrons between eachother!
• Define the words solute, solvent and solution


  -A solute is a substance that is dissolved in a solvent in a solvent, together they form a solution!
• Define miscible and immiscible


  -Miscible refers to the substances (particularly liquids) that mix together (eg. water and alcohol) - water and oil are immiscible ie. they do NOT mix
• Define soluble and insoluble


  Soluble refers to the subsrance that can be dissolved in a solvent - eg salt in water - insoluble substances wont dissolved in particular solvents!
• What are the columns of the periodic table called?

  Groups!