periodic table

• metalloids share some properties of nonmetals and some of metals
• at room temperature -

  • metals - solid except for mercury which is liquid
  • non metal- some solid , some gases, bromine is only liquid
  • metalloids - solid
• appearance -

  • metals- shiny lustre
  • non metals- not shiny
  • metalloids - can be dull or shiny
• conductivity -

  • metals - good conductors
  • non metals - poor conductors
  • metalloids - good and poor
• malleability and ductility -

  • metals - malleable and ductile
  • non metals- brittle and non ductile
  • metalloids - brittle and non ductile
• the period table is the chart that organizes all the elements according to their chemical and physical properties
• atomic mass is the average mass of the atom of an element
• atomic mass is written in decimal form and is measured in atomic mass unit (amu)
• the ion charge is the electric charge that forms on the atom when it loses or gains electrons
• an electrically charged atom is called an ion
• some elements have multiple ion charge they can form ions in more then one way
• the horizontal row in the periodic table is called a period and it is numbered from 1 to 7
• the vertical column is a helical family and they are numbered from 1 to 18
• • alkali metals - most reactive - 1
  • alkaline metals - very reactive - 2
  • halogens - very reactive - 17
  • noble gases- not reactive - 18
• a valence electron is an electron in the outermost not full shell
• a Bohr model diagram shows how many electrons are there in each shell
• the shell that contains the outermost electrons is called the valence shell
• compounds form through chemical bonds which are links between two or more atoms that hold the atoms together
• in covalent compounds, the atoms share electrons to form a molecule
• a molecule is a group of atoms which are bound together by sharing one or more pairs of electrons
• in ionic compound atom gain or lose electrons to form an ion
• negative charges attract positive charges
• ionic lattice is a repeating pattern of negative and positive ions
• a polyatomic ion is a group of atoms with a charge
• polyatomic ion includes both covalent bonds and ionic bonds
• chemical changes are the changes in which new substances are formed with new prperties
• physical changes occur when no new substance are formed, there is a change in appearance
• evidence for chemical changes -

  • colour change
  • heat , light or sound is produced
  • precipitate form
  • bubbles of gas form
• evidence of physical changes

  • tearing, grinding, cutting, ripping
  • changes of state
• reactants are the substance that are going to react
• product is the new substance that is formed by the chemical change
• endothermic reaction includes overall consumption of energy
• exothermic reaction includes overall release of energy in the forms of heat, light or sound energy
• ionic bonds contain a metal and a nonmetal