Chemistry edexcell

• Who discovered the nucleus and protons?

  Rutherford
• Who discovered neutrons?

  Chadwick
• What is the current model of the atom developed by Bore?

  It includes electrons in shells around a nucleus containing protons and neutrons
• What are the components of an atom and their charges?

  • Protons: mass of 1, charge of +1
  • Neutrons: mass of 1, charge of 0
  • Electrons: mass of 1/2000, charge of -1
• What does the atomic number represent?

  The number of protons in an atom
• How is the mass number calculated?

  It is the sum of protons and neutrons
• For calcium with an atomic number of 20 and a mass number of 40, how many neutrons does it have?

  20 neutrons
• What defines an isotope?

  An isotope has the same number of protons but a different number of neutrons
• How many protons and electrons do carbon isotopes have?

  Both carbon-12 and carbon-14 have 6 protons and 6 electrons
• How many neutrons does carbon-12 have?

  6 neutrons
• How many neutrons does carbon-14 have?

  8 neutrons
• Why does chlorine have a mass of 35.5?

  It is due to the relative abundance of its isotopes
• How do you calculate the average mass of chlorine isotopes?

  Use the formula: \frac{(37 \times 25) + (35 \times 75)}{100}
• What is the periodic table?

  A list of all known elements
• What is a compound?

  Two or more elements that are chemically bonded together
• Who was the first to attempt a periodic table?

  Newlands
• What was Newlands' method for arranging elements?

  He arranged them by mass and grouped them into octaves
• What was a key flaw in Newlands' periodic table?

  He did not leave gaps for undiscovered elements
• Who improved upon Newlands' periodic table?

  Mendeleev
• What was Mendeleev's key contribution to the periodic table?

  He left gaps for undiscovered elements
• What do groups in the periodic table indicate?

  The number of electrons in the outer shell
• What do periods in the periodic table indicate?

  The number of electron shells in an atom
• How many electrons can the first shell hold?

  2 electrons
• How many electrons can the second shell hold?

  8 electrons
• How many electrons can the third shell hold?

  8 electrons
• What happens to metals during ionic bonding?

  They lose electrons and form positive ions
• What happens to non-metals during ionic bonding?

  They gain electrons and form negative ions
• What charge do elements in group one form when they bond ionically?

  +1 ions
• What charge do elements in group two form when they bond ionically?

  +2 ions
• What charge do elements in group six form when they bond ionically?

  • 2 ions
• What charge do elements in group seven form when they bond ionically?

  • 1 ions
• What is ionic bonding?

  The transfer of electrons from a metal to a non-metal
• How does magnesium oxide form through ionic bonding?

  Magnesium transfers its electrons to oxygen
• What is the atomic number of sodium?

  11
• What happens to sodium when it forms an ion?

  It loses one electron and becomes positively charged
• What is the overall charge of a sodium atom?

  Zero, because protons and electrons cancel each other out
• What is sodium chloride?

  An ionic compound formed from sodium and chlorine
• What are the properties of ionic compounds?

  • High melting and boiling points
  • Conduct electricity when molten or dissolved
  • Form a giant ionic lattice structure
• What is covalent bonding?

  • The sharing of electrons between two non-metals
  • Forms small molecular structures
  • Examples include water (H2O) and methane (CH4)
• What is the formula for hydrochloric acid?

  HCl