ions

• Ion


  An electrically charged atom or group of atoms formed by the loss or gain of electrons
• Anion


  Negative ions that form when atoms gain electrons, meaning they have more electrons than protons
• Cation


  Positive ions that form when atoms lose electrons, meaning they have more protons than electrons
• All metals lose electrons to other atoms to become positively charged ions
• All non-metals gain electrons from other atoms to become negatively charged ions
• Neutral atom


  Has no overall charge
• Charged ion


  Has either gained or lost electrons, causing it to become charged
• Determining subatomic particles in ions

  1. Identify atomic (proton) number, mass (nucleon) number and charge

  2. Positively charged ion has lost electrons and has fewer electrons than protons

  3. Negatively charged ion has gained electrons and has more electrons than protons
• The number of electrons that an atom gains or loses is the same as the charge
• Formation of ions


  Loss or gain of electrons to obtain a full outer shell of electrons
• The electronic structure of ions of elements in groups 1, 2, 3, 5, 6 and 7 will be the same as that of a noble gas
• For exam purposes, only show the outer electrons in dot and cross diagrams
• When writing about ions, use the notation 1-, 2+ etc. to describe the charge, with the number first followed by the sign (+/-)
• Ionic compounds


  Contain metal and non-metal elements joined together as particles called ions
• Naming ionic compounds


  • The metal element's symbol is always written first
  • The non-metal element always takes on the name ending '– ide' unless oxygen is also present
  • When oxygen is present the name ending is usually '-ate'
• Examples of ionic compound names

  • PbS is called lead sulfide
  • MgCl2 is called magnesium chloride
  • CuSO4 is copper sulfate
  • KClO3 is potassium chlorate
  • Na2CO3 is sodium carbonate
• Deducing formulae of ionic compounds

  • The formulae can be calculated if you know the charge on the ions
  • You have to balance the charge of each part by multiplying each ion until the sum of the charges = 0
• Example of deducing formula

  • For aluminium sulfate: Al3+ and SO42-
  • Balance the charges: Al3+ x 2 = +6 and SO42- x 3 = -6
  • So the formula is Al2(SO4)3
• Another method to deduce formulae is to 'swap the numbers' of the charges
• Ionic compounds


  Contain metal and non-metal elements joined together as particles called ions
• Metal element's symbol


  Always written first
• Non-metal element


  Always takes on the name ending '– ide'
• When oxygen is present

  The name ending is usually '-ate'
• Deducing formulae of ionic compounds


  Requires balancing the charge of each ion until the sum of the charges = 0
• Common ions and their charges

  • Al3+
  • SO42-
• Steps to deduce formula of aluminium sulfate

  1. Write out the formulae of each ion, including their charges

  2. Balance the charges by multiplying them out

  3. The formula is Al2(SO4)3
• Another method to deduce formulae is to 'swap the numbers' of the charges
• Nucleon number


  The total number of protons and neutrons in an atom's nucleus
• Isotope


  A variant of an element that has the same number of protons but a different number of neutrons
• Isotope example


  Carbon-12 and carbon-14 are isotopes of the element carbon. Both have 6 protons, but carbon-12 has 6 neutrons and carbon-14 has 8 neutrons.