paper 1

• Elements are arranged by increasing atomic number.
• ionic bonding is between a metal and a non-metal, where the metal loses electrons to form a positive ion
• covalent bonds occur when two atoms share one or more pairs of electrons
• molecular substances consist of molecules held together only by intermolecular forces
• ionic compounds have high melting points due to strong electrostatic attraction between oppositely charged ions
• molecular substances have low melting points as they do not contain strong forces holding them together
• covalent bonding is between non metals
• electrolysis is used to extract a metal that is more reactive than carbon so reduction cant be used
• the cons of electrolysis is that it is expensive as it requires a lot of energy, uses fossil fuels and gives of co2
• at the negative electrode(cathode) hydrogen is always produced unless the metal is less reactive. in which case, the less reactive metal is formed
• at the positive electrode(anode) oxygen is always produced unless the solution contains halide ions, then the halogen is produced(group 7)
• in electrolysis, anions are reduced at the cathode (negative) and oxidised at the anode (positive)
• relative atomic mass= ( abundance of isotope 1 * mass of isotope 1) + ( abundance of isotope 2 * mass of isotope 2) / 100
• daltons model of the atom was atoms as solid spheres that could not be divided in to smaller parts
• the plum pudding model was a sphere of positive charge with negative electrons embedded in it
• rutherfords alpha scattering experiment showed that most of the mass of an atom was concentrated in a small dense nucleus
• thompsons theory of matter was that atoms contained negatively charged particles surrounded by positively charged particles
• chadwick discovered neutrons by bombarding beryllium with alpha particles and observing protons being ejected from lithium
• nuclear fission occurs when a heavy nucleus splits into two lighter ones releasing energy
• in the alpha scattering experiment it was found that some particles were deflected which showed that an atoms mass and positive charge must be concentrated in one small space
• the nuclear model is a dense nucleus with electrons orbiting it in shells
• james chadwick discovered the neutron
• an element is a substance made of one type of atom
• a compound is a substance made up of two or more elements chemically combined
• a mixture is a substance that contains two or more different elements or compounds that are not chemically combined
• isotopes are atoms of the same element with different numbers of neutrons
• relative mass is the average mass of all the atoms of an element