Chemistry 2.
- Created by: Abbs11_
- Created on: 03-05-16 17:00
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- Chemistry 2.
- Atomic structure and the periodic table.
- Particles.
- Protons are heavy and positively charged.
- Neutrons are heavy and neutral (no charge).
- Electrons are tiny and negatively charged.
- Isotopes are; different atomic forms of the same element, which have the same number of protons but different numbers of neutrons.
- Periodic table.
- Elements in the same group have similar properties. This is because they have the same number of electrons in their outer shell.
- The columns of the periodic table are called groups.
- The properties of elements (such as reactivity) often gradually change as you go down a group (as the atomic number increases).
- The elements are arranged in order of increasing atomic number along each row.
- The rows of the periodic table are called periods.
- Elements in the same group have similar properties. This is because they have the same number of electrons in their outer shell.
- Particles.
- Ionic compounds and analysis.
- In ionic bonding, atoms transfer (lose or gain) electrons to form positively or negatively charged atoms (or groups of atoms) called ions.
- Insoluble salts.
- To make pure, dry sample of an insoluble salt, you can use a precipitation reaction.
- Flame tests.
- sodium ions (Na+) give a yellow/orange flame.
- Potassium ions (K+) gives a lilac flame.
- Calcium ions (Ca2+) give a brick-red flame.
- Copper ions (Cu2+) gives a blue/green flame
- Testing for negative ions.
- Testing for carbonates- check for co2 by bubbling the gas through limewater, if the water turns milky we know co2 is present.
- Test for sulphates- for sulfate add dilute HCL followed by barium chloride solution if a white precipitate is created then we know the original compound was a sulfate.
- Test for chlorides- add dilute nitric acid followed by silver nitrate solution. A chloride gives a white precipitate of silver chloride,
- Covalent compounds and separation techniques.
- Atoms make covalent bonds by sharing a pair of electrons between two atoms.
- 1) This way both atoms feel that they have a full outer shell, and that makes them happy.
- 3) Each atom involved has to make enough covalent bonds to fill up its outer shell.
- 4) When atoms make covalent bonds with one or more other atoms, they form a molecule.
- 2) This way both atoms feel that they have a full outer shell, and that makes them happy.
- Simple molecular covalent substances.
- These make very strong covalent bonds to form small molecules of two or more atoms.
- The forces of attraction between these molecules are very weak.
- Melting and boiling points are very low because the molecules are easily parted from each other.
- Giant molecular covalent substances.
- All the atoms are bonded to each other by strong covalent bonds.
- They have very high melting and boiling points.
- They're usually insoluble in water.
- Except for graphite, they don't conduct electricity.
- Immiscible = liquids that won't mix.
- Miscible = liquids will mix.
- Mixtures of miscible liquids can be separated by fractional distillation.
- Miscible = liquids will mix.
- Atoms make covalent bonds by sharing a pair of electrons between two atoms.
- Groups in the periodic table.
- Metals are on the left and middle of the periodic table.
- Only elements on the far right of the table are non-metals.
- Transition metals are found in the centre block.
- These have high melting points.
- Form very colourful compounds.
- The elements in group 1 get more reactive as the atomic number increases.
- Alkali metals are soft and have low melting points.
- Group 7- very reactive.
- Chlorine is a fairly reactive, poisonous, dense green gas.
- Bromine is a dense, poisonous, orange liquid.
- Iodine is a dark grey crystalline solid.
- Group 0- the noble gases, they're colourless don't react much, non -flammable, hard to observe.
- Metals are on the left and middle of the periodic table.
- Chemical reactions.
- Exothermic.
- An exothermic reaction is one which overall gives out energy to the surroundings in the form of heat, shown by a rise in temperature.
- Rate of reaction.
- Affected by: temperature, surface area, catalyst, concentration
- A catalyst is a substance which changes the speed of a reaction, without being used up in the reaction.
- Collision theory.
- Particles have to collide in order to react, and they have to collide hard enough.
- More collisions increases the rate of reaction.
- Higher temperature increases collisions.
- Higher concentration increases collisions.
- Larger surface area increases collisions.
- Catalysts increase the amount of successful collisions.
- Faster collisions are only caused by increasing the temperature.
- Particles have to collide in order to react, and they have to collide hard enough.
- Endothermic.
- An endothermic reaction is one which overall takes in energy from the surroundings int eh form of heat, show by a fall in temperature.
- Exothermic.
- Atomic structure and the periodic table.
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