Atomic Structure

• diagram of an atom

  
• the 3 changes in state diagram...

  
• Solids:

  • have a fixed shape and cannot flow, because their particles cannot move from place to place
  • cannot be compressed (squashed), because their particles are close together and have no space to move into
• Liquids:

  • flow and take the shape of their container, because their particles can move around each other
  • cannot be compressed, because their particles are close together and have no space to move into
• Gases:

  • flow and completely fill their container, because their particles can move quickly in all directions
  • can be compressed, because their particles are far apart and have space to move into
• Water has a melting point of zero degrees Celsius but what is the boiling point?

  100 degrees Celsius
• atom economy =Mr Of DESIRED PRODUCT /Mr OF TOTAL PRODUCTS × 100
• in atom economy the higher the percentage the less waste product. 100% would mean no waste product.
• Elements are arranged into groups (columns) based on their electron configuration
• relative atomic mass


  the massive number on the element periodic table.
• An atom has a central nucleus. This is surrounded by electrons arranged in shells.
• number of protons=6, neutrons=6, electrons 12-6=6

  
• in carbon the mass number is 12 as its the massive number, carbons atomic number is 6 as it is the smaller number.

  
• states of matter table

  
• what are molecules?


  A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds
• why did mendeleev leave gaps?


  he believed undiscovered elements would eventually fill those gaps.
• what was bohrs model of the atom


  The Bohr model (named after Danish physicist Niels Bohr) of an atom has a small, positively charged central nucleus and electrons orbiting in at specific fixed distances from the nucleus. Electrons are not allowed to orbit in the space between these specific fixed orbits.
• nuclear model of the atom


  Rutherford's atomic model became known as the nuclear model. In the nuclear atom, the protons and neutrons, which comprise nearly all of the mass of the atom, are located in the nucleus at the center of the atom. The electrons are distributed around the nucleus and occupy most of the volume of the atom.
• plumb pudding model of the atom


  J.J. Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons. Thomson proposed the plum pudding model of the atom, which had negatively-charged electrons embedded within a positively-charged "soup."

  
• how did mendeleev order elements?


  Mendeleev developed the periodic table by organising the elements based on their atomic mass and chemical properties. 
• why was mendeleev's periodic table not accepted?


  he was unable to tell the location of a hydrogen atom in the periodic table
• what did jj Thompson develop?


  J. J. Thomson discovered electrons
• what did Rutherford discover?

  Rutherford had discovered the nuclear atom, a small, positively-charged nucleus surrounded by empty space and then a layer of electrons to form the outside of the atom
• what did Bohr discover


  a model of the atom in which the electron was able to occupy only certain orbits around the nucleus
• what did Chadwick discover?


  Chadwick is best known for his discovery of the neutron
• full timeline of the discoveries of the atom

  
• Atoms contain electrons, neutrons and protons. Write these three particles in order of their discovery...


  electron discovered first, then proton, then nuteron
• Describe the plum pudding model of the atom.


  a ball of positive charge with (negative) electrons embedded
• Nanoparticles of titanium dioxide are used instead of fine particles of titanium dioxide for coating self-cleaning windows. Suggest two reasons why


  a thinner coating is needed, have a higher surface area to volume ratio, less (material) needed (for the same effect), more light gets through
• how does the silver nanoparticles that are added to underwaer stop the development of bacteria and make them smell nicer for longer?


  Silver nanoparticles release silver ions, Silver ions kill bacteria or prevent their growth, Fewer bacteria means less odor production, This helps the underwear stay fresher for longer
• One disadvantage of nanoparticulate sunscreens is that they tend to clump together, making them difficult to apply. Suggest another disadvantage of these sunscreens.


  It may be more difficult to tell where sunscreen has been applied if it is invisible on the skin (or) relatively new so therefore could be potential danngers
• Silver has antibacterial properties. Nanoparticulate silver is used in some dressings for wounds. Suggest a possible hazard to the environment of silver nanoparticles.


  The silver nanoparticles could harm or kill useful bacteria in the environment when these dressings are thrown away after use.
• what are nanoparticles?

  Nanoparticles are tiny particles between 1 and 100 nanometers (nm) in size.
• Describe the advantages of using nanoparticles in sun creams


  improved UV-blocking efficiency due to their increased surface area-to-volume ratio. 
• what is a molecule?

   a group of two or more atoms bonded together.
• what are the 3 states of matter?

  Solid: Fixed shape and volume; particles are closely packed and vibrate in place. Liquid: Fixed volume but no fixed shape; particles are close but can move past each other. Gas: No fixed shape or volume; particles are far apart and move freely.
• what is solubility?

  How well a substance dissolves in a solvent (e.g., water).
• element vs mixture vs compound

  Element: a substance that is made up of only one type of atom. Compound:a substance that is made up of more than one type of atom bonded together. Mixture: a combination of two or more elements or compounds which have not reacted to bond together.
• why was the plumb pudding model disproved?

  The model couldn’t explain the results of Rutherford’s experiment, which showed that atoms have a small, dense nucleus at their center, disproving the “pudding” of positive charge.
• Atoms contain electrons, neutrons and protons. Write these three particles in order of their discovery.

  1. Electron (discovered in 1897 by J.J. Thomson)

  2. Proton (discovered in 1917 by Ernest Rutherford)

  3. Neutron (discovered in 1932 by James Chadwick)