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.