T1

• J.J Thompson created the 'plum-pudding model' of the atom. He said that atoms contain smaller, negatively charged particles - electrons.
• After J.J Thompson was Rutherfords model. If plum pudding was correct, the particles would go straight through the sheet or atleast a little deflected. But, most particles went through, some deflected at slight angles and some were deflected at angles greater than 90. Plum pudding was not right. In the middle is a small, positively charged nucleus and around was a cloud of negative electrons. Most of the atom is empty space.
• After Rutherford, was Bohr's model. Suggested that electrons were in shells.
• Protons:

  Relative mass = 1

  Relative charge = +1
• Neutrons:

  Relative Mass= 1

  Relative Charge= 0
• Electrons:

  Relative Mass: 0.0005 (very small)

  Relative Charge: -1
• Dalton model:


  Dalton described atoms as solid spheres, stating that different spheres made up the different elements.
• Structure of an atom: as a nucleus containing protons and neutrons, surrounded by electrons in shells
• Explain why atoms contain equal number of protons and electrons

  Atoms are neutral and the charges on a proton are +1 and on an electron are -1, therefore amount of protons = amount of electrons, so that the charges cancel
• The nucleus of an atom is very small compared to the overall size of the atom
• Most of the mass of an atom is concentrated in the nucleus
• Mass number: The total number of protons and neutrons in an atom's nucleus.
• Isotopes:

  Different forms of the same element, which have the same number of protons (atomic number) but different number of neutrons (mass number)
• Relative Atomic Mass: average mass of one atom. Relative atomic mass is calculated using the abundance of different isotopes and because it is an average it can lead to the relative atomic mass not being a whole number.
• R.A.M. = (mass of isotopeA x % of isotopeA) + (mass of isotopeB x % of isotopeB) /100
• Describe how Mendeleev arranged the elements

  He ordered his table in order of atomic mass, but not always strictly – i.e. in some places he changed the order based on atomic weights. Left gaps for elements that he thought had not been discovered yet
• Describe how Mendeleev used his table to predict the existence and properties of some elements not then discovered

  Mendelev realised elements with similar properties belonged in the same groups in the periodic table so was able to leave gaps and place the discovered elements where they fit best. Elements with properties predicted by Mendeleev were later discovered and filled the gaps
• Explain that Mendeleev thought he had arranged elements in order of increasing relative atomic mass but this was not always true because of the relative abundance of isotopes of some pairs of elements in the periodic table

  Knowledge of isotopes made it possible to explain why the order based on atomic weights was not always correct, because some elements have a higher mass than others when isotopes are taken into account, but a lower one if you only look at one specific isotope
• Explain the meaning of atomic number of an element in terms of position in the periodic table and number of protons in the nucleus

  Elements are arranged in order of atomic (proton) number (bottom number) and so that elements with similar properties are in columns, known as groups. Elements in the same group have the same amount of electrons in their outer shell, which gives them similar chemical properties.
• elements are arranged in order of increasing atomic number, in rows called periods and elements
• elements with similar properties are placed in the same vertical columns called groups
• Metals = elements that react to form positive ions. They loose electrons. They are found on the left side of the periodic table
• Non-metals = elements that do not form positive ions. Instead they gain electrons so form negative ions. Found on the right side.
• electronic configurations

  the electronic configuration of an element tells you how many electrons are in each shell around an electron’s nucleus. The first shell holds only 2 electrons. The next shells hold upto 8. Atoms gain/loose to form a full outer shell and become ions.
• Explain how the electronic configuration of an element is related to its position in the periodic table


  group an electron is in tells you how many electrons are in its outermost shell aka group 1 elements have 1 electron in their outer shell. (so they have to loose one and become +1 charged). period an electron is in tells you which number shell an element's outermost electron is found in aka period 3 elements have their outermost electrons in shell 3. (number of shells)
• Explain how the electronic configuration of an element is related to its position in the periodic table


  group => electrons on outer shell

  period=> number of shells
• Anion:


  A negatively charged ion. Formed when an atom gains electrons.
• Cation:

  A positively charged ion. Formed when an atom loses electrons.
• Explain how ionic bonds are formed


  When a metal and non-metal react, the metal atom looses electrons to have a full outershell, and forms a positive ions (cation). The non-metal gains these electrons and forms a negative ion (anion). Electron transfer during the formation of an ionic compound can be represented by a dot and cross diagram
• Ionic bonding: strong electrostatic force of attraction between positive cation and negative anions.
• Ion: A charged atom or molecule that has gained or lost electrons.
• Explain the formation of ions in ionic compounds from their atoms, limited to compounds of elements in groups 1, 2, 6 and 7

  Ions produced by metals in Groups 1 and 2 and by nonmetals in Groups 6 and 7 have the electronic structure of a noble gas (Group 0). this means group 1 metals will lose 1 electron and form +1 ions. group 2 metals will lose 2 electrons and form +2 ions. group 6 nonmetals will gain 2 electrons and form 2- ions. group 7 nonmetals will gain 1 electron and form 1- ions, remember a compound will have an overall charge of 0 so you need to balance out the + and - charges
• Explain the use of the endings –ide

  -ide means the compound contains 2 elements
• Explain the use of the endings -ate

  -ate means the compound contains at least 3 elements, one of which is oxygen
• Explain the use of the endings –ide and –ate in the names of compounds

  these endings are used for the negatively charged ions in a compound
• Water= H2O
• Ammonia= NH3
• Carbon Dioxide= CO2
• Hydrogen= H2
• Chlorine= Cl2