Atomic structure and the periodic table

• What is the smallest part of an element that can exist?

  Atom
• What is the approximate radius of an atom?

  Around 0.1 nanometres
• What did John Dalton believe about atoms before the discovery of the electron?

  That they were tiny solid spheres that could not be divided
• What defines an element?

  Contains only one type of atom
• How many different elements are there approximately?

  Around 100
• What is a compound?

  Two or more elements chemically combined
• How can compounds be separated into elements?

  Only by chemical reactions
• What was the plum pudding model proposed by JJ Thomson?

  A ball of positive charge with negative charges embedded in it
• What did Rutherford's alpha particle scattering experiment demonstrate?

  That mass was concentrated at the center of the atom
• What is the central nucleus of an atom composed of?

  Protons and neutrons
• What is the charge of a proton?

  +1
• What is the charge of a neutron?

  0
• What is the charge of an electron?

  • 1
• What did Niels Bohr propose about electrons?

  That they orbit the nucleus at specific distances
• What is the mass number of an atom?

  The sum of the protons and neutrons in the nucleus
• What is the atomic number of an atom?

  The number of protons in the atom
• How are mixtures defined?

  Two or more elements or compounds not chemically combined together
• How can mixtures be separated?

  By physical processes
• What are the methods of separating mixtures and their descriptions?

  • Filtration: Separates an insoluble solid from a liquid (e.g., sand from saltwater).
  • Crystallisation: Separates a solid from a solution (e.g., pure crystals of sodium chloride).
  • Simple distillation: Separates a solvent from a solution (e.g., pure water from saltwater).
  • Fractional distillation: Separates a mixture of liquids with different boiling points (e.g., compounds in crude oil).
• What are isotopes?

  Atoms of the same element with the same number of protons and different numbers of neutrons
• What is chromatography used for?

  To separate substances that move at different rates through a medium
• What are the groups of elements in the periodic table?

  • **Alkali metals**: Group 1, very reactive with water and oxygen.
  • **Transition metals**: Found in the center of the periodic table.
  • **Halogens**: Group 7, form negative ions.
  • **Noble gases**: Group 0, inert and non-reactive.
• How are elements arranged in the periodic table?

  In order of atomic number
• What do elements in the same group have in common?

  They have the same number of outer shell electrons
• What do elements in the same period have in common?

  They have the same number of electron shells
• What are the properties of metals in the periodic table?

  Form positive ions, conductors, high melting and boiling points, ductile, malleable
• What did Mendeleev contribute to the periodic table?

  He left gaps for undiscovered elements and predicted their properties
• What are the properties of non-metals in the periodic table?

  Form negative ions, insulators, low melting and boiling points
• What happens when alkali metals react with water?

  They form a metal hydroxide and hydrogen
• What is the general reaction of alkali metals with oxygen?

  Metal + oxygen → metal oxide
• What is the general reaction of halogens with metals?

  Metal + halogen → metal halide
• What is the result of a more reactive halogen displacing a less reactive halogen?

  It forms a new halide and releases the less reactive halogen
• How do boiling points change in group 7 elements?

  Boiling points increase down the group
• What is the significance of the law of conservation of mass in chemical equations?

  The total mass of products equals the total mass of reactants
• What is the process of crystallisation used for?

  To obtain pure crystals from a solution
• What is the purpose of fractional distillation?

  To separate a mixture of liquids with different boiling points
• What is the significance of the atomic structure in chemistry?

  It helps to understand the properties and behavior of elements and compounds
• How does the arrangement of elements in the periodic table reflect their properties?

  Elements are arranged by atomic number, showing trends in properties
• What is the role of electrons in chemical bonding?

  Electrons are involved in forming bonds between atoms
• What is the relationship between atomic number and the number of electrons in a neutral atom?

  The number of protons equals the number of electrons