chemistry

• aqueous solution


  The mixture made by adding soluble substances to water
• atom


  The smallest part of an element that can still be recognised as that element
• atomic number


  The number of protons which equals the number of electrons in an atom it is sometimes called the proton number.
• balanced symbol equation 


  A symbol equation in which there are equal numbers of each type of atom on either side of the equation.
• compound


  A substance made when two or more elements are chemically bonded together
• electron


  A tiny particle with negative charge. Electrons orbit the nucleus of atoms or ions in shell
• electronic structure 


  A set of numbers to share the arrangement of electrons in their shells or energy levels
• group


  Who are the elements in the column labelled 1 to 0 in the periodic table
• ion


  a charged particle produced by the loss or gain of electrons
• isotope


  atoms that have the same number of protons with different numbers of neutrons. they have the same atomic number but different mass numbers
• law of conservation of mass


  The total mass of the products formed in a reaction is equal to the total mass of the reactants
• mass number


  The number of protons plus neutrons in the nucleus of an atom
• Neutron


  a dense particle found in the nucleus of an atom it is neutral so it has no charge
• Noble gases


  The very unreactive gases found in group 0 of the periodic table that atoms have a very stable electronic structure
• nucleus


  The very small dense central part of an atom that contains protons and neutrons
• periodic table


  An arrangement of elements in the order of their atomic numbers forming groups and periods
• product


  A substance made as a result of a chemical reaction
• proton


  A tiny positive particle found inside the nucleus and at atom
• reactant


  substance we start with before chemical reaction takes place
• shell

  an area in an atom around its nucleus where electrons are found
• alkali metals


  group 1 metals
• what are the alkali metals called this

  they react with water to form alkali solutions
• halogens


  group 7 metals
• How is the periodic table ordered

  By atomic number
• how were the early list of elements ordered

  by atomic mass
• Why did Mendeleev leave gaps in his periodic table?

  Leave room for elements that had not yet been discovered.
• why do elements in a group have similar chemical properties 


  they have the same number of electrons in the outer shell