Chemistry Unit 1-3 by Elena https://padlet.com/elenakots/chemistryrevisionunits123 Chemistry Revision for mock exams en-us 2017-04-14 08:14:06 UTC 2023-06-02 21:44:19 UTC hello@padlet.com Atoms elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166353190 - All substances are made up of atoms
- Elements consist of one type of atom chemically bonded together
- Compounds are made up of two or more different types of atom chemically bonded together]]> 2017-04-14 08:18:09 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166353190 Chemical Equations elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166353464 - The total mass of the reactants = the total mass of the products
- You can include state symbols to give extra information in balanced symbol equations. (s) --> solid; (l) --> liquid; (g) --> gas; (aq) --> aqueous.]]> 2017-04-14 08:24:23 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166353464 Separating Mixtures elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166353637 - A mixture is made up of two or more different substances that are not chemically combined together
- Mixtures can be separated by physical means. i.e. Filtration, crystallisation, simple distillation, fractional distillation and chromatography.]]> 2017-04-14 08:27:23 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166353637 Fractional Distillation and Paper Chromatography elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166353902 (refer to page 10-11 in your textbook)]]> 2017-04-14 08:33:30 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166353902 History of the Atom elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166353942 - Thomson's plum pudding model of the atom only acknowledged the electrons of an atom
- He believed there were free flowing electrons in a sphere of positively charged matter.
- Geiger and Marsden concocted the alpha particle scattering experiment that disproved the plum pudding theory.
- Rutherford suggested that the positive charge of an atom must be concentrated in the centre of the atom. Thus the discovery of protons.
- Niels Bohr discovered that electrons orbit around the nucleus at set distances, in different fixed energy levels.
- James Chadwick did an experiment that could only be explained by the existent of neutrons as nothing else explained the missing mass that had been noticed in atoms]]> 2017-04-14 08:34:24 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166353942 Structure of the atom elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166356228 Atomic number: the number of protons.
Mass number: total of protons and neutrons.
The number of protons is always the same as the number of electrons]]> 2017-04-14 09:22:01 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166356228 Ions, Atoms, and Isotopes elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166356290 - Atoms that gain electrons form negative ions. If atoms lose electrons they form positive ions.
- You can represent the atomic number and mass number of an atom using the notation:
24 Mg
12
Where magnesium's atomic number is 12 and its mass number is 24.
- Isotopes are atoms of the same element with the different numbers of neutrons. They have identical chemical properties, but their physical properties, such as density, can differ.]]> 2017-04-14 09:23:42 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166356290 Electronic structure elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166356477 - The electrons in an atom are arranged in energy levels or shells.
- The lowest energy level can hold up to two electrons and the 2nd and 3rd shell can hold up to 8 electrons.
- The 4th shell starts to fill after the 3rd energy level.]]> 2017-04-14 09:28:51 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166356477 Development of the Periodic Table elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166356599 - John Newlands produced the periodic table based on the "Law of Octaves". He arranged each element in order of mass and noticed that each 8th element has similar properties.
- He didn't take into consideration the fact that there are still some undiscovered elements. His table only really worked up until calcium.
- Medeleev's table left gaps for the unknown elements, which when discovered, matched his predictions, and so his table was accepted by the scientific community. He arranged them in order of the elements' atomic number (proton number).]]> 2017-04-14 09:31:33 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166356599 The Periodic Table according to Electronic Structures elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166357073 - The number of electrons in the outermost shell of an atom determines its chemical properties.
- The group number = electron number on outermost shell.
- Atomic number determines its position in the periodic table.
- The noble gases in Group 0 are inert (don't react) because of their very stable electron arrangements.
- Metals lose electrons in reactions where as non-metals gain electrons.]]> 2017-04-14 09:40:19 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166357073 Groups in the Periodic Table elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166357218 (refer to page 26-29 in your textbook) (and for explaining trends refer to page 31) (i don't think its on the exam)]]> 2017-04-14 09:45:00 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166357218 The Transition Elements elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166357611 - Physical Properties
 > They are good conductors of electricity and thermal energy
 > They are hard and strong
 > They have high densities
 > They have high melting points (with the exception of mercury which is a liquid at room temp.)
- Chemical Properties
 > The transition elements are much less reactive than the elements in group 1
- Compounds of Transition Elements
 > Many of the transition elements form coloured compounds.  i.e.:
    } copper (II) sulfate is blue due to its copper ions
    } nickel (II) carbonate is pale greenn due to its nickel ions
    } chromium (III) oxide is dark green due to its chromium atoms
    } manganese (II) chloride is pale pink due to its manganese ions

-The name of a compound containing a transition element usually includes a Roman number. e.g. Copper (II) sulfate

- Transition metals are important industrial catalysts

]]> 2017-04-14 09:53:44 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166357611 States of Matter elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166359581 - There are 3 states of matter: solid, liquid and gas.
- If you don't know what their properties are, refer to page 37, the key points.]]> 2017-04-14 10:34:15 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166359581 elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166359953 2017-04-14 10:42:08 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166359953 Ionic Bonding elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166359987 Ionic bonding occurs between positive and negative ions, which attract each other and bind together to form ionic compounds. For example, sodium chloride consists of Na+ ions and Cl- ions bound together.

Each ion is surrounded by oppositely charged ions held in place by electrostatic attraction and forming an ionic crystal lattice. The ions in a crystal lattice are very strongly bonded - a high temperature is required to melt the crystal.
]]> 2017-04-14 10:42:47 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166359987 Covalent Bonding elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166359998 A covalent bond is formed between non metal atoms, which combine together by sharing electrons. Covalent compounds have no free electrons and no ions so they don't conduct electricity.

The Periodic Table is an arrangement of the elements in order of atomic number. Elements in the same vertical column are in the same group or family and have similar chemical properties.
]]> 2017-04-14 10:42:57 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166359998 Metallic Bonding elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166360852 Metals form giant structures in which electrons in the outer shells of the metal atoms are free to move. The metallic bond is the force of attraction between these free electrons and metal ions. Metallic bonds are strong, so metals can maintain a regular structure and usually have high melting and boiling points.]]> 2017-04-14 11:01:29 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166360852 Giant Ionic Structures elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166360982 - It takes a lot of energy to break the many strong ionic bonds, operating in all directions, that hold a giant ionic lattice together. So ionic compounds have high melting points. They are all solids at room temperature.
- Ionic compounds will conduct electricity when molten or dissolved in water. This is because their ions can then become mobile and can carry charge through the liquid.]]> 2017-04-14 11:03:40 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166360982 Giant Covalent Structures elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166361072 - Some covalently bonded substances have giant structures thus their melting and boiling points are very high.
- Graphite contains giant layer of covalently bonded carbon atoms. However there are no covalent bonds between the layers. This means that they can slide over each other, making graphite soft and slippery. The carbon atoms in diamond have a rigid giant covalent structure, making it a very hard substance.
- Graphite can conduct electricity and thermal energy because of the delocalised electrons that can move along its layers.]]> 2017-04-14 11:06:37 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166361072 Giant Metallic Structures elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166361470 - Metals can be bent and shaped because the layers of atoms (or positively charged ions) in a giant metallic structure can slide over eachother.
- Alloys are harder than pure metals because the regular layers in a pure metal are distorted by atoms of different sizes in an alloy.
- Delocalised electrons in metals enable electricity and thermal energy to be transferred through a metal easily.]]> 2017-04-14 11:17:50 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166361470 Fullerenes and Graphene elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166361812 - Fullerenes are made up of carbon and they can form large cage-like structures and tubes based on hexagonal rings of carbon atoms.
- Graphene is a single layer of graphite and so it is one atom thick. Both graphene and fullerenes are useful for the industry.
-  For example: fullerenes are finding uses as transport mechanism for drugs to specific sites in the body, as catalysts, and as reinforcement for composite materials. Graphene has excellent electrical conductivity and it will help develop the electronics industry in the future.]]> 2017-04-14 11:26:15 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166361812 Nanoparticles elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166362106 - Nanoscience --> study if small particles that are between 1 and 100 nanometres in size.
- They have different properties than the same material in bulk as they have a high surface area to volume ratio, with a high percentage of atoms exposed at their surface.
- Nanoparticles may result in smaller quantities of materials, such as catalysts, needed for industrial processes.]]> 2017-04-14 11:32:13 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166362106 Nanoparticles elenakots https://padlet.com/elenakots/chemistryrevisionunits123/wish/166362108 - Nanoscience]]> 2017-04-14 11:32:18 UTC https://padlet.com/elenakots/chemistryrevisionunits123/wish/166362108