Topic 1 - Atomic Structure and the Periodic Table

• An atom is the smallest part of an element that can exist.
• Compounds are made from two or more different elements (types of atoms) combined together in fixed proportions.
• An element is a substance with only one type of atom.
• The rows in the periodic table are called periods.


  Elements show a gradual change in properties across a period
• The columns in the periodic table are called groups and contain similar elements
• Atoms consist of protons, neutrons and electrons
• Protons have a positive charge (+), Neutrons do not carry any electrical charge (0) and Electrons have a negative charge (-)
• A mixture consists of two or more elements or compounds not chemically combined together.
• Mixtures can be separated by physical processes such as filtration, crystallisation, simple distillation, fractional distillation and chromatography.
• What separation technique is shown in the diagram?

  
• What separation technique is shown in the diagram?

  
• What separation technique is shown in the diagram?

  
• What separation technique is shown in the diagram?

  
• The discovery of the electron led to the plum-pudding model
• scattering experiments led to the plum-pudding model being replaced by the nuclear model.
• Neils Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances.
• The experimental work of James Chadwick provided the evidence to show the existence of neutrons within the nucleus.
• the number of electrons is equal to the number of protons.
• Atoms are arranged in the modern periodic table in order of their atomic number (proton number).
• The total number of protons and neutrons in an atom is called its mass number.
• Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes of that element.
• The first energy level can hold a maximum of 2 electrons, the 2nd and 3rd can hold up to 8. (not really true for 3rd ).
• Elements in the same group in the periodic table have the same number of electrons in the highest energy levels (outer electrons).
• The elements in Group 0 of the periodic table are called the noble gases.
• The elements in group 1 of the periodic table are called the alkali metals.
• The elements in group 7 of the periodic table are called the halogens.
• A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt.
• In group 1, the further down the group an element is the more reactive it becomes. As the atoms get larger the outer electron is further from the nucleus. Thus the outer electron is less attracted to the nucleus and so can more easily be lost.
• In group 7, the further down the group an element is the less reactive it becomes. As the atoms get larger the outer electrons are further from the nucleus. Thus the electron from another element is much harder to gain.