ATOMIC STRCUTURE

• what are compounds?


  two or more elements chemically combined in fixed proportions
• what are mixtures?

  two or more elements or compounds not chemically combined together
• what are five separation processes?


  - filtration

  - crystallization

  - simple distillation

  - fractional distillation

  - chromatography
• how does filtration work?

  it separates an insoluble solid from a liquid reaction mixture using filter paper
• how does crystallization work?

  it separates a soluble solid from a liquid reaction mixture using an evaporating dish and filter paper
• how does simple distillation work?

  it separates a liquid from a solution by heating the liquid at its boiling point and condensing the separated vapor
• how does fractional distillation work?

  it separates a mixture of liquids using a fractioning column, separating the different liquids at their boiling points
• what is an overview of the development of the model of the atom?

  1. tiny spheres that could not be divided

  2. ball of positive charge with negative electrons embedded (plum pudding)

  3. mass of the atom was concentrated in a charge nucleus at the center (alpha particle scattering)

  4. electrons orbit at specific distances (niels bohr)

  5. positive charge could be divided into protons

  6. existence of neutrons (james chadwick)
• who thought of the plum pudding model and what was the theory?


  john dalton; it suggested that the atom is a ball of positive charge with negative electrons embedded in it

  
• who conducted the alpha particle scattering experiment and what was it?


  ernest rutherford; he fired positively charged alpha particles at a thin sheet of gold
• why did the alpha particle scattering experiment lead to a new nuclear model?

  they were expecting the particles to pass straight through or be slightly deflected by the sheet; instead, more particles were deflected than expected and some were deflected backwards
• what was the new nuclear model after the alpha particle scattering experiment?

  there's a positively charged nucleus at the center, where most of the mass is concentrated; it's surrounded by a cloud of negative electrons

  
• what is the relative charge and mass of a proton?

  +1, 1
• what is the relative charge and mass of a neutron?

  0, 1
• what is the relative charge and mass of an electron?

  -1, very small
• how do you find the number of electrons in an atom?

  number of protons, atomic number
• what is the radius of atom?

  0.1 nm (1 × 10⁻¹⁰)
• what is the radius of a nucleus?

  less than 1/10,000 of the radius of an atom (1 × 10⁻¹⁴)
• what is the mass number of an atom?


  the sum of the protons and neutrons
• what are isotopes?

  atoms of the same element that have the same number of protons but different number of neutrons
• what is relative atomic mass?

  an average value that takes account of the abundance of the isotopes of the element
• how do you calculate relative atomic mass?

  sum of (isotope abundance × isotope mass number) / sum of abundances of all isotopes
• what are the maximum numbers of the first three shells in an atom?

  1: 2

  2: 8

  3: 8
• how is the periodic table arranged?


  by atomic number
• what are groups?

  - columns of elements with similar properties

  - number of electrons in the outer shell
• what are periods?


  - rows of elements with the same number of full shells
• what are the steps in the development of the periodic table?

  1. classified by atomic weight, some elements were placed in inappropriate groups

  2. mandeleev left gaps and switched up the order a bit

  3. new elements were discovered and knowledge of isotopes explained why atomic mass order was incorrect
• what are metals?

  elements that react to form positive ions
• what are non-metals?

  elements that react to form negative ions
• what are the elements from group 0 called?

  noble gases
• what are the properties of the noble gases?


  - unreactive

  - colorless

  - monatomic

  - flammable
• what are the trends as you go down group 0?

  - increasing boiling point

  - increasing relative atomic mass
• what are the elements from group 1 called?

  alkali metals
• what are the properties of alkali metals?


  - reactive

  - soft
• what are the trends as you go down group 1?

  - increasing reactivity

  - lower melting and boiling points

  - higher relative atomic mass
• how do alkali metals react with water?

  vigorously to produce hydrogen gas and metal hydroxides
• how do alkali metals react when heated in chlorine gas?

  vigorously to form white metal chloride salts
• how does lithium react with oxygen?

  forms lithium oxide (Li₂O)
• how does sodium react with oxygen?

  forms a mixture of sodium oxide (Na₂O) and sodium peroxide (Na₂O₂)
• how does potassium react with oxygen?

  forms a mixture of potassium peroxide (K₂O₂) and potassium superoxide (KO₂)