Chemistry paper 1

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


  An atom
• What defines an element?


  An element contains exactly the same type of atoms
• What is a compound?


  A substance that contains two or more elements that are chemically combined
• How are the elements in a compound present?


  In fixed proportions
• What is the chemical formula for carbon dioxide?


  CO₂
• What is a mixture?


  A substance that contains two or more elements or compounds that are not chemically combined
• How can mixtures usually be separated?


  By physical techniques such as filtering and distillation
• What is an example of a mixture?

  Air
• What are the techniques for separating mixtures?


  • Filtration: Separating an insoluble solid from a liquid
  • Evaporation: Separating a soluble solid from its solution
  • Distillation: Separating a liquid from a solution
• Who proposed the plum pudding model of the atom?


  1. J. Thomson
• What did the plum pudding model suggest about the structure of the atom?


  The atom consisted of positive 'dough' with negative electrons stuck in it
• What experiment did Rutherford conduct to test the plum pudding model?


  He directed a beam of alpha particles at a thin gold leaf
• What were the results of Rutherford's experiment?


  Most particles passed through, some were deflected by large angles, and some deflected straight back
• What does the nucleus of an atom contain?


  Protons and neutrons
• What is the relative mass of a proton?


  1
• What is the relative charge of an electron?


  • 1
• How is most of the mass of an atom concentrated?

  In its nucleus
• What are the relative masses and charges of subatomic particles?


  • Proton: Relative mass = 1, Relative charge = +1
  • Neutron: Relative mass = 1, Relative charge = 0
  • Electron: Relative mass = very small, Relative charge = -1
• What is the atomic number of an element?


  The number of protons in an atom of that element
• How does the atomic number relate to the number of electrons in an atom?


  Atoms contain equal numbers of protons and electrons
• What is the atomic number of sodium?


  11
• What is the mass number of an atom?


  The total number of protons and neutrons in an atom
• How do you calculate the number of neutrons in an atom?


  Mass number - atomic number
• Calculate the number of neutrons in a sodium atom with a mass number of 23.


  12
• Calculate the number of neutrons in a bromine atom with a mass number of 80.


  45
• What is the electron structure of an atom?


  • Electrons occupy energy levels (electron shells) outside the nucleus
  • Different shells hold different maximum numbers of electrons
  • Electrons fill the lowest available energy level first
• What is the maximum number of electrons in the first shell?


  2
• What is the maximum number of electrons in the second shell?


  8
• What is the maximum number of electrons in the third shell?


  8
• How can the electronic structure of an atom be predicted?


  From its atomic number
• What is the electronic structure of sodium?


  2,8,1
• How is the electronic structure linked to the periodic table?


  • Group Number: Number of electrons in the outermost shell
  • Period Number: Number of electron shells
• What is the group number of sodium?


  1
• What is the period number of sodium?


  3
• What is the significance of Mendeleev's periodic table?


  • Arranged elements by increasing atomic weights
  • Considered properties of elements and compounds
  • Left gaps for undiscovered elements
  • Showed elements with similar properties in groups
• What did Mendeleev do with elements that had similar chemical properties?


  He lined them up in groups
• What was a limitation of Mendeleev's periodic table?


  Some pairs of elements were in the wrong order due to atomic weights
• How are elements arranged in the modern periodic table?


  In rows (periods) by increasing atomic number and in columns (groups) by similar properties
• What is the relationship between electronic structure and the periodic table?


  • Group Number: Number of electrons in the outermost shell
  • Period Number: Number of electron shells
• What are the Group 1 elements called?


  Alkali metals