chemistry

• molecule = two or more atoms that are covalently bonded
• simple molecular substances have low melting and boiling points because the forces that hold the molecules together are weak and easily broken
• the larger the molecule, the higher the melting and boiling point are
• molecules don't conduct electricity or heat
• molecules are poor conductors of electricity because there are no charged particles or free electrons to move and carry heat
• 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
• molecule diagram

  
• 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
• does not conduct electricity = no charged particles
• Ions do not conduct electricity when in a solid state because the ions are not free to move and carry charge
• Ions have a high melting point as they are made up of giant ionic structures lots of energy is needed to break the millions of ionic bonds
• As the particles are heated they gain electrons. This makes them vibrate more and more until they have enough energy to escape from the lattice structure
• Model Ionic binding answer:

  Lithium loses 1 electron and forms a 1+ ion. Fluorine gains this electron and forms a 1- ion. Opposite charged ions attract electrostatically to each other. This is an Ionic bond
• 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.
• simple molecular substances have low melting points and boiling points because the forces that hold the molecules together are weak and easily broken
• the larger the molecule, the higher the mp and bp
• simple molecular structures do not conduct electricity or heat
• 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
• how to do ionic bonding equations?

  • write your symbols
  • assign the charges
  • drop and swap the numbers but not the charges
  • if the numbers can be cancelled down, do so
• ionic bonding occurs when a metal and nonmetal react, metals form positive ions and nonmetals for negative ions
• what is a chemical bond?

  this involves atoms combining to form chemical compounds and bring stability to the resulting product
• Ionic compounds are held together by electrostatic forces between the oppositely charged ions
• ionic compounds are in a giant lattice structure and are held together by strong electrostatic forces of attraction between oppositely charged ions
• properties of graphite

  • soft
  • very high melting point
  • very high boiling point
  • insoluble in water
  • good electrical conductor
• in covalent bonding, atoms share electrons with each other.
• non metals form covalent bonds because they need to share electrons to make a full outer shell.
• when they are gases, most nonmetals form simple molecules where two atoms are joined together