Atomic Structure And The Periodic Table

• what is an atom?

  The smallest part of an element that can exist
• What is the basic structure of an atom?

  central nucleus, surrounded by electrons which orbit around the nucleus on rings.
• What is the nucleus made up of?

  Protons and neutrons
• what is an ion?

  An ion is an atom that has gained or lost electrons, meaning that the charge no longer balanced which results in a positive or negative charge.
• what is the atomic number of an element?

  the number of protons and electrons
• what is the mass number of an element?

  total number or neutrons and protons
• how do you find out how many neutrons an element has?

  Subtract the atomic number from the atomic mass.
• what is an isotope?

  An isotope is a type of an element that has the same number of protons but a different number of neutrons in its nucleus.
• what is a compound and how is it formed?

  a compound is a combination of two or more elements in fixed proportions. Formed through chemical reactions.
• what is a mixture?

  A combination of two or more substances that are not chemically bonded.
• how are mixtures separated?

  physical processes such as filtration, distillation, chromatography.
• What was Democritus's Theory?

  The idea that everything is made up from tiny particles that cant be broken down any further and are separated by empty space (500BC)
• What was Jhon Dalton's Theory?

  He suggested that different types of solid spheres might make up different elements (1800s)
• What was JJ. Thomson's Theory?

  Plum pudding model (1897) He believed that atoms couldn't be solid spheres and instead must've contained negatively charged particles (known as electrons). He proposed that the atom was a general ball of positive charge with discrete electrons in it.
• How did Ernest Rutherford disprove JJ. Thomson's theory?

  Gold foil experiment (1909) He did an experiment where he took positively charged alpha particles and fired them at a thin sheet of gold. His idea was that if Thomson's theory that the positive charge in gold atoms was generally spread out then the alpha particles should pass through. Instead some were deflected to the side and a small amount were deflected back the way they came from, disproving Thomson's theory.
• What was Ernest Rutherford's Theory?

  Nuclear atom model (1909) He proposed that there was a compact nucleus witch contained all of the positive charge of the atom. So the negative charge must exist in a cloud around the nucleus.
• What was Niels Bohr's theory?

  suggested that the electrons orbit around the nucleus on shells. Hi theory was important as the orbiting of the electrons is what prevents the atom from collapsing.
• Who discovered protons?

  Ernest Rutherford figured out the positive charge of the nucleus is made up of small discrete particles (protons)
• what is the relative atomic mass?

  The weighted average mass of an element's isotopes.
• What is the formula for relative atomic mass?

  sum of (isotope Abundance x isotope mass) divided by sum of Abundance of all isotopes
• How are the elements in the periodic table organized?

  By atomic number and properties. Also elements in the same group have the same number of electrons in the outer shell which gives them similar properties.
• what was the periodic table like before it was fully developed?

  Before the discovery of protons, neutrons and electrons, elements were arranged by their atomic weights.

  The early periodic tables were incomplete and some elements were

  placed in inappropriate groups.
• How did Mendeleev help organize the early periodic table?

  Mendeleev overcame some of the problems by leaving gaps for

  elements that he thought had not been discovered and in some

  places changed the order based on atomic weights.

  Elements with properties predicted by Mendeleev were discovered

  and filled the gaps. Knowledge of isotopes made it possible to

  explain why the order based on atomic weights was not always

  correct.
• how did Mendeleev help organize the early periodic table?

  Mendeleev overcame some of the problems by leaving gaps for

  elements that he thought had not been discovered and in some

  places changed the order based on atomic weights.

  Elements with properties predicted by Mendeleev were discovered

  and filled the gaps. Knowledge of isotopes made it possible to

  explain why the order based on atomic weights was not always

  correct.
• metal and non metal periodic table placement?

  Metal: to the left and bottom of the periodic table

  Non-metal: to the right and top of the periodic table
• what is a molecule?

  A group of atoms bonded together. Also the smallest unit into which a substance can be broken down without chemical change.
• group 7 properties?

  • Halogens have similar reactions as they all have 7 electrons in their outer shell
  • none metals and consist of molecules made of pairs of atoms
  • molecular mass, melting and boiling points increase going down the group
  • reactivity decreases going down the group.
• group 1 metals?

  • Alkali metals are reactive
  • have one electron on their outer shell
  • reactivity increases going down the group.
• group 0 metals?

  • Noble gases are unreactive
  • 8 electrons in outer shell (apart from helium which has 2)
  • boiling points increase with increasing relative atomic mass.