Atomic structure

• What is an atom?

  The smallest part of an element that can exist

  
• What is an element?

  a Substance that contains only ONE type of atom.
• What are molecules?

  Substances made up of more than one atom of element chemically bonded together
• What is a compound?

  Substances made up of more than one type of element chemically bonded in fixed proportions
• How are compounds formed?

  Conpounds are formed from elements by chemical reactions that always involved the formation of one or more new substances
• What happens when chemical reactions are made?

  Energy is released into the atmosphere
• What happens when chemical bonds are broken?

  energy is absorbed from the surroundings
• What reactions transfer energy to their surroundings

  Reactions that transfer energy to their surroundings are called exothermic reactions. Temperature is often observed as increasing
• Examples that transfer exothermic reactions

  Combustion of fuel

  Reaction of metal acid
• What reactions require a gain in energy

  Reactions that require a gain in energy from their surroundings are called endothermic reactions. Temperature is often observed as decreasing
• Examples of endothermic reactions

  Thermal decomposition,

  photosynthesis,

  denaturing an enzyme.
• What are isotopes?

  Atoms of the same element with the same number of protons and electrons but different numbers of neutrons
• Atomic structure

  
• Relative atomic mass

  Elements average mass value that takes account of the the abundance of each isotope of an element. The symbol for relative mass is Ar