Atomic structure + periodic table

• 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 element listed and approximately how many are there? They are listed in the periodic table; there are approximately 100.
• Elements can be classified into two groups based on their properties; what are these groups? Metals and non-metals
• Elements may combine through chemical reactions to form new products; what are these new substances called? Compounds
• What is a compound? Two or more elements combined chemically in fixed proportions 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? Does it have the same chemical properties as its constituent materials? A mixture consists of two or more elements or compounds not chemically combined together; it does have the same chemical properties
• What are the methods through which mixtures can be separated (there are five)? Do these involve chemical reactions? Filtration, crystallisation, simple distillation, fractional distillation and chromatography; they do not involve chemical reactions
• Describe and explain simple distillation. Simple distillation is used to separate liquid from a solution – the liquid boils off and condenses in the condenser. The thermometer will read the boiling point of the pure liquid. Contrary to evaporation, we get to keep the liquid.
• What is fractional distillation used for?

  It is a technique for separation of a mixture of liquids.
• How does fractional distillation work?


  It works when liquids have different boiling points.
• What is the main difference between fractional distillation and simple distillation?

  • Fractional distillation uses a fractionating column.
  • Fractional distillation separates liquids with closer boiling points.
  • Simple distillation is used for liquids with significantly different boiling points.
• What additional component is found in the apparatus for fractional distillation compared to simple distillation?

  A fractionating column is added on top of the heated flask.
• What is the purpose of the glass beads in the fractionating column?


  They help to separate the compounds.
• How does the temperature gradient in the fractionating column affect the separation of liquids?

  • The column is hot at the bottom and cold at the top.
  • Liquids condense at different heights based on their boiling points.
  • This allows for effective separation of components in the mixture.
• In an industrial setting, what happens to the mixtures during fractional distillation?

  Mixtures are repeatedly condensed and vaporized.
• Why is it important that the column is hot at the bottom and cold at the top in fractional distillation?

  This temperature gradient allows liquids to condense at different heights based on their boiling points.
• Describe and explain filtration Filtration is used to separate an insoluble solid is suspended 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 an apparatus for separating immiscible liquids. Two immiscible liquids of different densities will form two distinct layers in the separatory funnel. We can run off the bottom layer (the liquid with greater density) to a separate vessel.
• Describe the plum-pudding model The atom is a ball of positive charge with negative electron embedded in it.
• Describe the Bohr/nuclear model and how it came about The nuclear model suggests that electrons orbit the nucleus at specific distances (shells) – it came about from the alpha scattering experiments
• Later experiments led to the discovery of smaller, positive particles in the nucleus; what are these particles 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: 1, 1, very small ; Charges: 1, 0 , -1 (respectively)
• Explain why atoms are electrically neutral. They have the same number of electrons and protons
• What name is 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
• What is the mass number? The total number of protons and neutrons
• Where is the majority of mass of an atom? The nucleus
• How does one calculate the number of neutrons using mass number and atomic number? Subtract the atomic number from the mass number
• What is an isotope? Do isotopes of a certain element have the same chemical properties? Atoms of the same element (same proton number) that have a different number of neutrons.
• 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.
• What are ions? Ions are charged particles. They are formed when atoms lose electrons (positive ions) or gain (negative ions) electrons.
• What is formed when a metal reacts with a non-metal? An 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 each other (cf. ionic compounds).
• Explain the following: solute, solvent, solution, miscible, immiscible, soluble, insoluble. A solute is a substance that is dissolved in a solvent. Together, they form a solution. Miscible refers to the substances (particularly liquids) that mix together, e.g. water and alcohol. Water and oil are immiscible, i.e. they do not mix. Soluble refers to the substance that can be dissolved in a solvent, e.g. salt in water. Insoluble substance won’t dissolve in a particular solvent.
• The rows of the periodic table are called…? Periods