atomic structure

• more reactive halogens displace less reactive ones in a compound
• chlorine = greenish yellow gas, is toxic
• bromine = orange brown liquid, toxic
• iodine = grey solid, purple gas when sublimates , toxic
• reactivity decreases down group 7
• larger atoms have more shells
• lithium's reaction with water = fizzing, moving around on surface, floating, dissolving
• sodium's reaction with water = vigorous fizzing, floats, melts into a ball
• group one metals react vigorously with group 7 halogens to form white compounds
• ionic compounds are formed when metals react with non-metals
• metals form positive ions and non-metals for negative ions
• losing electrons = +1
• gaining electrons = -1
• why do all group 7 elements act in a similar with hydrogen?

  all group 7 elements are missing one electron in their outer shell, therefore only requiring one to fill it.
• group 7 reactivity?

  • reactivity decreases as you go down the group
  • in larger atoms there are more shells
  • the outermost electrons are further rom the nucleus
  • they are shielded by inner shells
  • this makes it harder to gain an electron as it will be less strongly attracted to the nucleus
• halogens use displacement reactions
• atoms are neutral and ions carry a charge
• transition metals

  • high density
  • compounds are coloured
  • useful as catalysts
  • strong and hard
  • high melting points
  • not very reactive
  • form different ions
• positive 1+ ions

  • hydrogen H+
  • potassium K+
  • silver Ag+
  • Sodium Na+
  • Copper (I) Cu+
• Negative 1- ions

  • bromide Br-
  • Chloride Cl-
  • Iodide I-
  • Fluoride F-
  • Hydroxide OH-
  • Nitrate NO3-
• Positive 2+ ions

  • Calcium Ca2+
  • Copper II Cu2+
  • Iron II Fe2+
  • Magnesium Mg 2+
  • Zinc Zn2+
• Positive 3+ ions

  • Aluminium Al3+
  • Iron III Fe3+
• Negative 2- ions

  • Oxide o2-
  • Carbonate CO3(2-)
  • Sulfate SO4(2-)
• Acid formulae


  Hydrochloric acid = HCL

  Sulfuric acid = H2SO4

  Nitric acid = HNO3
• the nucleus


  1. contains protons and neutrons
  2. has a radius of 1x10^-4
  3. has a positive charge
  4. whole mass concentrated in nucleus
• the electrons


  1. move around the nucleus in electron shells
  2. are negatively charged
  3. have no mass
• number of protons = number of electrons

  1. atoms are neutral as they have the same amount of protons and electrons
• protons and neutrons have a relative mass of 1, electrons have nearly 0 mass
• protons have a charge of +1, neutrons have no charge and electrons have a charge of -1
• mass number is the total protons and neutrons
• an isotope is an atom with the same number of protons but a different amount of neutrons
• to find the number of neutrons in an atom, subtract the atomic number from the mass number
• relative atomic mass is an average mass taking into account the different masses and abundances of al the isotopes making up the element.
• compounds are substances formed from two or more elements and held together by chemical bonds
• a compound formed from a metal and a non-metal is an ion
• a compound form from non-metals is covalently bonded. each atom shares an electron with another atom.
• a mixture consists of two or more elements or compounds not chemically combined together, therefore they are easily physically separated by filtration crystallisation, fractional distillation and chromatography. no new substances are made in a mixture
• Who proposed that atoms were solid spheres?

  John Dalton
• What did John Dalton say about atoms?

  Each atom is a solid sphere of different elements
• What year did J.J. Thompson propose his model of the atom?

  1897