elements and compounds

• everything that exits is made up of atoms
• elements are made up of only one type of atom
• each element have a symbol on the periodic table
• compound - two or more different types of atoms bonded together to form a new substance with its own properties
• molecule - two or more atoms joined by chemical bonds
• ionic compound - formed when metal loses electrons to non-metal, resulting in positively charged ion (cation) and negatively charged ion (anion)
• ionic compound - formed when metals react with non-metals, they lose electrons forming positive ions (cations) and gain electrons forming negative ions (anions)
• ionic compound - formed when metal loses electrons to non-metal, resulting in positive ion (cation) and negative ion (anion)
• mixture - substances which can be separated into their original components without changing them chemically
• element - pure substance made up of only one type of atom
• atom - smallest particle that makes up an element
• elements that are found in group 8 or 0 are called the noble gases such as helium or argon
• oxygen is a molecule however it is still an element because its atoms come in pairs
• atomic number -this tells us how many protons are in the nucleus of the atom

  relative atomic- mass this gives us a an idea of how heavy on atom is

  A) relative atomic mass

  B) atomic number

  
• chemical reactions

  the chemicals that we begin with do the reacting these are called the reactants

  the chemicals that are made or produced are called the products
• th atom contains protons nuetrons and electrons
• the number of electrons are always equal to the number of protons
• if an atom loses electrons it is positively charged
• if an atom gains electrons it is negativley charged
• isotopes are atoms of the same element just with a diffrent number of nuetrons in the nucleus
• if the electronic configuration was 2.8.7 this shows us that the element sits in group 7 on the periodic table
• the reactivity increases down the group 1 as the outer electron shell is further from the nucleus
• group 1 = lithum soduim potassuim
• physical properties of group 1 = low melting points less dence in water soft can be cut by a knife
• chemical properties of group 1 = reactive metals stored in paraffin oil to stop oxygen and water reacting with them
• group 7 elements are called halogens and they are very reactive
• group 7 = halogens (fluorine, chlorine, bromine, iodine, astatine)
• group 7 physical properties =melting and boiling points increase down the group , vapours become darker as you move down the group
• group 7 chemical properties = dissolve in water forming acid solution , universal indicator goes brick red, stored in paraffin oil to prevent reaction with water
• group 0 elements are called noble gases and are non-metals. They are inert and do not react with other elements.
• group 0 = heluim neon argon
• filltration = filtration of insoulble particles through a filter paper to remove solid particles from a liquid
• crystillisation = a process of separating a soluble solid from a liquid
• simple distilliation= water is boiled and the vapour is cooled and condensed
• chromotography = a technique used to separate mixtures of substances based on their solubility
• rf value = distance travelled (the highest number on the ruler) / distance travelled (the number the dye mesures on the ruler )
• persentage of element in compound = ar *number of atoms / the mr =*100
• moles = mass of substance / Mr of substance
• mass = moles x Mr (Mr = Mr of element)
• the inner core = hottest point of earth made from iorn and nickle