chemistry

• how are elements organised on the periodic table?

  in order of increasing atomic number
• the periodic table is used to determine weather or not an element is?

  a metal or non-metal
• groups in the periodic table contain what?

  contain elements with the same number if outer electrons, this is indicated by the group number
• what do elements within a group have?

  - the same valency

  - similar chemical properties -> as they have same number of electrons in their outer energy shells
• what is the pattern for electron arrangement (first 20 elements)?

  2,8,8,2
• what does an atoms nucleus contain?

  protons + neutrons
• what orbits the atom?

  electrons
• what charge do protons have? what mass do protons have?

  positive +1

  1 amu
• What charge do electrons have? what mass do electrons have?

  negative -1

  0 amu
• what charge do neutrons have? what mass do neutrons have?

  neutral (no charge)

  1 amu
• what is the atomic number?


  the number of protons in an atom
• in a neutral atom what are equal?

  the number of electrons and protons
• what is the mass number?

  the number of protons + number of neutrons
• what are isotopes?


  atoms with the same atomic number but different mass numbers/ atoms with same number of protons but different numbers of neutrons
• what is nuclide notation used to show?

  - show the atomic number, mass number and charge of atoms (ions)

  - you can then determine the number of protons, neutrons and electrons from this
• how many isotopes do most elements have?

  most have two or more
• what do covalent bonds form between?

  between non-metal atoms
• when is a covalent bond

  When two positive nuclei are held together by their common attraction for a shared pair of electrons
• What is a diatomic element?


  elements that exist naturally as pairs (contains two atoms of the same element (x^2))
• what are the 7 diatomic elements

  hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine
• what is this molecule described as (draw linear)?


  a linear molecule
• what is this molecule described as (draw angular)?


  a angular/bent molecule
• what is this molecule described as (draw pyramidal)?


  a pyramidal molecule
• what is this molecule described as (draw tetrahedral)?

  a tetrahedral molecule
• when more than one bond is form what does it lead to?

  a double or triple covalent bond
• covalent substances can form what?

  either discrete molecular or giant network structures
• what do covalent molecular substances have/do or don't do?

  - strong covalent bonds within the molecules + only weak attractions between the molecules

  - low melting + boiling points as only weak forces of attraction between the molecules are broken when a substance changes state

  - do not conduct electricity as they do not have charged particles which are free to move

  - are insoluble in water may dissolve other solvents
• what do covalent network structures have/do or don't do?

  - have a network of strong covalent bonds within one giant structure

  - have very high melting + boiling points as the network of strong covalent bonds is not easily broken

  - do not dissolve

  - in general do not conduct electricity as they do not have charged particles which are free to move
• when are ions formed?

  when atoms lose or gain electrons to obtain the stable electron arrangement of a noble gas
• what happens to metal atoms when forming positive ions?

  lose electrons
• what happens to non-metal atoms when forming negative ions?

  gain electrons
• What can ion-electron equations be written to show?

  the formation of ions through loss or gain of electrons
• what type of attraction are ionic bonds?

  electrostatic attraction between positive + negative ions
• what structures do ionic compounds form?

  lattice structures of oppositely charged ions with each positive ion surrounded by negative ions + each negative ion surrounded by positive ions
• what melting + boiling points do ionic compounds have?

  high melting + boiling points as strong ionic bonds must be broken in order to break up the lattice
• Are ionic compounds soluble in water?

  yes - as they dissolve the lattice structure breaks up allowing water molecules to surround the separated ions
• Do ionic compounds conduct electricity?

  Only when molten or in solution as the lattice structure breaks up allowing the ions to be free to move
• how can conduction in ionic compounds be explained?

  by the movement of ions towards oppositely charged electrodes
• what does rate of reaction affect?

  affects productivity- the amount of product made in a fixed amount of time
• what can increase rates of reaction?


  increase of temperature, increase in concentration of reactant, increase surface area/decreasing particle size, use of catalyst