Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
18 Cards in this Set
- Front
- Back
|
Ionic compounds |
Formed by loss or gain of electrons. Held together by strong electrostatic charges. In a regular repeating lattice structure. Often form crystals Ionic compounds are neutral, so made of a negative charged and positive charged ions (*never write atoms) |
|
|
Features of ionic compounds |
High boiling and melting points due to strong electrostatic bonds. Conduct electricity when molten or dissolved in water, but not solid- particles must be charged and free to move around. It is important to remember that it is the ions moving that enable ionic compounds to conduct electricity and that it is NOT electrons moving. |
|
|
Covalent bonds |
Molecular substances are held together by using covalent bonds Usually form between non metals Are produced by sharing pairs of electrons |
|
|
How to find molecular formula |
1) find out how many electrons the atom needs to make a full outer shell. 2) this number is the same as the valency. 3) match up the number of valencys (if hydrogen has a valency of 1, and oxygen has a valency of 2, 1 x 2 = 2 which Is equal to the oxygen valency of 2- so the answer is H2O |
|
|
What is a molecule? |
A molecule is when 2 or more atoms of an element is chemically joined. |
|
|
What is the difference from a molecule and a compound? |
A molecule is when 2 or more atoms of an element is chemically joined. Are groups of atoms joined by covalent bonds. Molecules can be compounds or elements Molecule example: -water (H2O) -oxygen (O2) Compound example: -salt (NaCl) -water (H2O) |
|
|
Allotropes of carbon- fullerenes |
Carbon atoms are covalently bonded to 3 or more carbon atoms Often tubular molecules (nanotubes) or spherical- eg buckmibsterfullerene (or Bucky ball) which has 60 carbon atoms that form a ball with the formula C60. |
|
|
Allotropes of carbon- fullerenes |
Carbon atoms are covalently bonded to 3 or more carbon atoms Often tubular molecules (nanotubes) or spherical- eg buckmibsterfullerene (or Bucky ball) which has 60 carbon atoms that form a ball with the formula C60. |
|
|
Allotropes of carbon- Graphene |
Similar to fullerenes but is not a simple molecule. Consists of a sheet of carbon atoms with no fixed formula. Sheet is just one atom thick but it’s bonds make it extremely strong. Also allows free electrons to move across surface so it is a good electrical conductor. GRAPHENE- a single sheet of carbon with free electrons that can conduct electricity. |
|
|
Allotropes of carbon- fullerenes |
Carbon atoms are covalently bonded to 3 or more carbon atoms Often tubular molecules (nanotubes) or spherical- eg buckminsterfullerene (or Bucky ball) which has 60 carbon atoms that form a ball with the formula C60. Is soft and slippery due to strong bonds within molecule but weak forces between molecules. |
|
|
Allotropes of carbon- giant structures of carbon (diamond and graphite) |
Both have high melting points due to strong covalent bonds. Graphite has 3 bonds per atom whilst diamond has 4. This means graphite has a layers structure and means not all atoms are held in covalent bonds. These delocalised electrons are free to move and can carry an electric current- used in electrodes. The sheets in graphite are held together by weak forces so layers slide pass each other. Used for lubricant. Diamond is very hard due to rigid network of carbon atoms in a tetrahedral arrangement, joined by strong covalent bonds. Used for tools to cut things and as an electrical insulator as no free charged particles. |
|
|
Properties of metal |
STRUCTURE AND BONDING: all same size and closely packed to form giant lattice. Metals have 1,2 or 3 electrons on outer shell. These are lost from each atom and become free to move about. Causes lattice of positive metal ions to be surrounded in a sea of delocalised electrons. Have strong bonds so have high melting and boiling points. MALLEABILITY- Are malleable as when hit by hammer, the layer of ions slide over each other CONDUCT ELECTRICITY- When a potential difference (voltage) is applied between 2 points on a price or metal the electrons will flow towards the positive side. This flow transfers energy and forms an electrical current. The electrical conductivity increases as the number of delocalised electrons increases. |
|
|
Bonding models- ionic |
WHERE FOUND: in most compounds containing metal and non-metal atoms. BONDING: ionic bonds formed by the loss and gain of electrons to produce oppositely charged ions that attract one another. STRUCTURE: billions of ions held together in a lattice structure PROPERTIES: -high melting/boiling points -many are soluble in water -conduct electricity when liquid or in solution but don not when solid |
|
|
Bonding models- simple molecular (covalent) |
WHERE FOUND: in most non-metal elements and compounds. BONDING: covalent bonds formed when atoms share pairs of electrons. STRUCTURE: small distinct groups of atoms PROPERTIES: -low melting/boiling points -a few are soluble in water -most do not conduct electricity |
|
|
Bonding models- simple molecular (covalent) |
WHERE FOUND: in most non-metal elements and compounds. BONDING: covalent bonds formed when atoms share pairs of electrons. STRUCTURE: small distinct groups of atoms PROPERTIES: -low melting/boiling points -a few are soluble in water -most do not conduct electricity |
|
|
Bonding models- giant covalent |
WHERE FOUND: in a few non-metal elements and some compounds of non-metals. BONDING: covalent bonds formed when atoms share pairs of electrons. STRUCTURE: billions of atoms held together in a lattice structure. PROPERTIES: -high melting/boiling points -insoluble in water -most do not conduct electricity (except in carbon as graphite) |
|
|
Bonding models- metallic |
Where found: in all metals BONDING: all metallic bonds are the electrostatic attraction between positive metal ions and negative delocalised electrons. STRUCTURE: billions of ions held together in a giant lattice structure of positive ions in a ‘sea’ of negative delocalised electrons. PROPERTIES: -a high melting/boiling point -insoluble in water -conduct electricity when solid or liquid |
|
|
Problems with bonding models |
-dot and cross does not show structure formed. -metallic model does not show that the ions will be vibrating all the time. - 3D ball and stick models show atoms too far apart |
