Atomic structure and the periodic table

The Basics:

  • All substances are made of atoms.
  • An atom is the smallest part of an element that can exist.
  • Atoms of each element are represented by a chemical symbol, eg O represents an atom of oxygen, Na represents an atom of sodium.
  • There are about 100 different elements.
  • Elements are shown in the periodic table

Atoms can be split into smaller components:

  • Electrons
  • Neutrons
  • Protons
  • Each element has an atomic number and a mass number.
  • The mass number is located beneath the chemical symbol. This shows the sum of neutrons and protons.
  • The atomic number is located above the chemical symbol. This shows the number of protons. This is the same as the amount of electrons.

The Periodic Table :

  • The early periodic table
  • The Modern periodic table
  • Trends within the periodic table

http://www.bbc.co.uk/schools/gcsebitesize/science/triple_aqa/periodic_table/

Isotopes:

  • For most elements there are atoms with different numbers/amounts of neutrons.
  • Atoms with the same number of protons but a different number of neutrons are called Isotopes.
  • This means that isotopes have the same atomic number but a different mass number.

For example, carbon has three isotopes and so there are three different types of carbon atoms. These three isotopes are all carbon atoms because they all contain 6 protons, but they each have a different number of neutrons.

Important groups in the PERIODIC TABLE:

Group 0: NOBLE GASES

  • NOBLE GASES are elements in the periodic table that have stable electron structures, making them stable and nonreactive.
  • The elements are: Helium, Neon, Argon, Krypton, Xenon and Radon.
  • They are the furthest right column on the periodic table
  • Elements are ordered in order of protons increasing left to right. It can also be considered to be increasing in electron quantity, reaching a full shell once reaching the most right column, meaning they all have full shells
  • At room temperature, they are all colourless gases

Group 1: ALKALI METALS

  • ALKALI METALS are elements in the periodic table that have one electron on their outer shell.
  • The elements are: Lithium, Sodium, Potassium, Rubidium and Caesium.
  • They are the furthest left column on the periodic table
  • They are all soft metals, so they all can be cut with a knife. They are also highly reactive metals, which means that they have to be stored in jars of oil to stop reactions with water and oxygen.
  • At room temperature, they all appear to be silver-gray metals

Group 2: ALKALINE EARTH METALS

  • They are silvery, shiny, and relatively soft metals.
  • They are fairly reactive under standard conditions.
  • They have two outer valence electrons which they readily lose.
  • They all occur in nature, but are only found in compounds and minerals, not in their elemental forms.
  • They react with halogens to form compounds called halides.
  • All of them except beryllium react strongly with water.
  • They tend to form ionic bonds, except for beryllium which forms covalent bonds.

Group 3: TRANSITION METALS

  • They form coloured compounds
  • they are good conductors of heat and electricity
  • they can be hammered or bent into shape easily
  • they are less reactive than alkali metals such as sodium
  • they have high melting points - but mercury is a liquid at room temperature
  • they are usually hard and tough
  • they have high densities

Group 4: POST-TRANSITION METALS

  • In chemistry, post-transition metals are the metallic elements in the periodic table located between the transition metals (to their left) and the metalloids (to their right).
  • Usually included in this category are gallium, indium and thallium; tin and lead; and bismuth.
  • Which elements are counted as post-transition metals depends, in periodic table terms, on where the transition metals are taken to end and where the metalloids or non-metals are taken to start.

Group 5: METALLOIDS

  • They appear to be metal in appearance, but are brittle.
  • They can generally form alloys with metals. Some metalloids such as silicon and germanium become electrical conductors under special conditions. These are called semiconductors.
  • They are solids under standard conditions.
  • They are mostly nonmetallic in their chemical behaviour.

Group 6: NON-METALS

  • They are either gas (hydrogen, oxygen, nitrogen) or solid (carbon, sulfur) under standard conditions.
  • They are not good conductors of electricity or heat.
  • They are very brittle in their solid form.
  • They are not malleable or ductile. T
  • hey generally have lower densities than metals.
  • They generally have lower melting and boiling points than metals. The one exception to this is carbon.
  • They have high ionization energies.

Group 7: HALOGENS

  • Table salt, bleach, fluoride in toothpaste, chlorine in swimming pools—what do all of these have in common?
  • Add halogen lamps to the list, and the answer becomes more clear: all involve one or more of the halogens, which form Group 7 of the periodic table of elements. Known collectively by a term derived from a Greek word meaning "salt-producing," the halogen family consists of five elements: fluorine, chlorine, bromine, iodine, and astatine.
  • The first four of these are widely used, often in combination; the last, on the other hand, is a highly radioactive and extremely rare substance.
  • The applications of halogens are many and varied, including some that are dangerous, controversial, and deadly.