Structure and Bonding 1

Chemical Bonding 1.2
1. 2 or more elements react to form a compund
2. elements join together by sharing electrons or by transfering electrons
  1. forms a stable structure
    1. Example: Noble Gases
3. when 2 or more non-metal atoms join by sharing electrons they form covalent bonds
4. when a metal and non-metal element combine they form an ionic bond
  1. the metal atoms lose electrons to form positive ions
    1. the non-metal atom gains electrons so becomes positively charged
      1. oppositly charged ions attract each other in the ionic compound - ionic bonding
Ionic Bonding 1.1
1. hold oppositely charged ions together in giant structures
  1. very regular as the ions all pack together neatly
  2. strong electrostatic forces attract in all directions
    1. each ion is surrounded with ions of the opposite charge
      1. held firmly in place
2. chemical formula shows the different numbers of ions
  1. e.g. sodium chloride: NaCl contains equal numbers of ions
    1. the different ions alternate to form a cubic lattice
  2. ratio of ions in the structure depends on the charge of the ions
3. dot and cross diagrams are used to represent the ions in ionic bonds
  1. only show the electrons in the outermost shell
4. atoms loose or gain electrons - making them charged
  1. need to complete the outer shell
5. usually between a metal and non-metal atom
Formulae of ionic componds 1.3
1. Ionic compounds are neutral
2. by knowing the charge of each ion we can work out the formula by balancing the charges
  1. the charge of each ion can be worked out from the number of the group
  2. for transition metals the charge of the ion is shown by the roman numeral next to the symbol on the periodic table
  3. some ions are made of more than 1 element so you need to multiply the ions to write equation in brackets
Covalent Bonding 1.4
1. atoms share electrons to become stable - aren't charged
  1. each shared pair of electrons strongly attracts the atoms forming a covalent bond
2. usually between 2 non-metal atoms
3. substances held together by covalent bonds are called molecules
4. depending how many electrons the atom needs to fill the outer shell decides how many covalent bonds are formed
5. only acts between the atoms it holds together
  1. many covalent substances consist of small molecules
6. some atoms can form several bonds - e.g. carbon
  1. these can join together to form giant covalent structures which are often referred to as macromolecules
    1. diamond
    2. graphite
Metals 1.5
1. atoms in a metallic element are the same size
  1. form giant structures which are arranged in regular patterns
    1. the electrons on the highest energy level delocalise and move freely between atoms
      1. produces a lattice of positive ions in a 'sea' of moving electrons
      2. delocalised electrons strongly attract the positive ions and hold the giant structure together

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