atomic structure

Question 1

arranging electrons

Answer 1

first shell contains 2 electrons

the rest contain a maximum of 8 electrons

Question 2

ions

Answer 2

• formed when an atom gains or loses electrons
• atoms with incomplete outer shells are more unstable than those with full outer shell. they react to gain a ‘noble gas structure’
• metal lose e- and become +ively charged
• non-metals gain e- and become -ively charged

Question 3

ionic bonding

Answer 3

-positive ion: cation
-negative ion: anion-made by strong electrostatic forces between two oppositely charged ions.
these forces act in all directions

Question 4

dot and cross diagrams

Answer 4

-brackets- show charge

Question 5

properties of ionic compounds

Answer 5

• high melting and boiling point
• don’t conduct electricity when solid but do when molten or in solution
• crystalline
• hard but brittle
• soluble in water
• ions held in 3d lattice

Question 6

covalent bonding

Answer 6

• non metals form bonds together by sharing electrons-one shared electron pair makes a single covalent bond. two shared pairs makes a double covalent bond
• e.g. hydrogen has just one electron in its outer shell so the two atoms get together and share the electrons-now they both have a full outer shell

Question 7

simple covalent molecules

Answer 7

• the forces of attraction between the molecules are weak
• substances with the smallest molecules have the weakest intermolecular forces and are gases at room temperature
• Larger molecules have stronger attractions and so may be liquid at room temperature or solids with low melting points

Question 8

giant covalent structures

Answer 8

• every atom in the structure is joined to several other atoms by strong covalent bonds
• high boiling and melting points
• There are no charged ions- e.g. diamond and graphite

Question 9

diamond

Answer 9

• made up of carbon atoms
• carbon has four electrons in is outer shell
• to gain a full outer shell it must share 4 electrons
• each carbon atom forms 4 covalent bonds with 4 other carbon atoms

Question 10

properties of diamond

Answer 10

• high mpt and bpt
• rigid and hard due to lots of strong covalent bonds in a giant lattice
• does not conduct electricity
  silicon dioxide has similar properties to diamond

Question 11

graphite

Answer 11

• made up of carbon
• 4 electrons in its outer shell
• only uses 3 of its outer electrons in bonding
• each carbon atom forms 3 covalent bonds with 3 other carbon atoms
• unused electron; free moving between the layers of carbon

Question 12

properties of graphite

Answer 12

• high mpt and bpt
• soft slippery and can be used as a lubricant as it does not have a strong lattice arrangement and weak bonds between layers so layers can slide
• can conduct electricity as it has delocalised electrons which are able to move between the layers carrying charge which come from carbon atoms

Question 13

metallic bonding

Answer 13

• atoms in a metallic element are all the same size
• form giant structures in which the layers of atoms are arranged in regular patterns
• The electrons in the outer shell are delocalised and are free moving between the atoms
• produces a LATTICE of POSITIVE METAL IONS SURROUNDED BY A “SEA” OF FREE MOVING ELECTRONS
• they strongly attract the positive metal ions and hold the giant structure together
• formed due to the strong electrostatic forces of attraction between positive metal ions and delocalised electrons

Question 14

shape memory alloys

Answer 14

• these can be bent or deformed into a different shape

- when they are heated they return to their original shape

Question 15

properties of alloys

Answer 15

• stronger than pure metals because the particles disrupt the layers so slip cannot occur easily