Chemistry
- Created by: meganjane30
- Created on: 08-06-17 16:13
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- Periodic Table
- Mendeleve:
- Arranged elements in order of increasing mass & He left gaps for undiscovered elements.
- Today
- Arranged in order if increasing atomic number
- 18 groups & 7 periods
- Arranged in order if increasing atomic number
- Periodicity
- it refers to any repeating trends that are seen in the elements properties (in a period)
- Periodic Properties include Ionisation Energies, Electronegativity, Atomic Radius
- Ionisation Energies
- It is the energy required to remove one electron from one mol of gaseous atoms to form one mol of gaseous 1+ atoms
- Strong IE- strong attraction between nucleus& outer shell so more energy is required to overcome attraction & remove the electron
- Strong IE- strong attraction between nucleus& outer shell so more energy is required to overcome attraction & remove the electron
- Increases across a period due to more protons which means a higher nuclear charge so stronger attraction between outer electron & shell so more energy required
- Decreases down a group because increased electrons means increased shell number so shielding gets in the way and outer electrons are further from the nucleus so there is a weaker attraction so less IE id required
- EXCEPTIONS
- The drop between group 2&3 is due to sub shell structure
- In group 2 the outer electron is in an s-orbital whereas in group 3 the outer electron is in a p-orbital. Even though a p-orbital has slightly higher energy than an s-orbital, a p-orbital has shielding from the nucleus and so on average the p-orbital electron is found further from the nucleus hence the drop in IE
- The drop between group 5&6 is due to P-orbital repulsion
- In group 5 the electron is being removed from a single occupied p-orbital whereas in group 6 it is being removed from a shared orbital. The repulsion between the 2 electrons makes it easier to remove the electron from a shared orbital hence the drop in IE
- The drop between group 2&3 is due to sub shell structure
- You can use IE to predidc no of electrons in the outer shell, The group of the element or the identity of an element
- It is the energy required to remove one electron from one mol of gaseous atoms to form one mol of gaseous 1+ atoms
- it refers to any repeating trends that are seen in the elements properties (in a period)
- Group 7 Elements
- They exist as Diatomic molecules
- Each halogen has 7 electrons in their outer shell so are very reactive
- Halogens are OXIDISING AGENTS- It oxidises another species whilst itself gets reduced
- Fluorine is so reactive it is rarely found in its natural state
- Astatine is so radioactive its never found in its natural form
- Halogens are OXIDISING AGENTS- It oxidises another species whilst itself gets reduced
- A more reactive halogen will displace a less reactive halogen in a solution and when it reacts it forms a precipitate of the less reactive halogen
- To test which Halide ion is in solution: Add DILUTE NITRIC ACID to mystery solution then add SILVER NITRATE and a precipitate will form
- Chlorine = White, Bromine = Cream and Iodine = Yellow
- Then add DILUTE AMMONIA SOLUTION and if it dissolves it is a chloride
- Then add CONCENTRATED AMMONIA SOLUTION and if it dissolves its a bromine and if it remains its an iodide
- Then add DILUTE AMMONIA SOLUTION and if it dissolves it is a chloride
- Chlorine = White, Bromine = Cream and Iodine = Yellow
- They DISPROPORTINATE
- CHLORINE +( cold aqueous )NaOH = Sodium Chlorate(1) Solution = BLEACH
- Chlorine + Water = HCl + HClO( chloric(I) Acid
- HClO + Water = chlorate(I) ions (ClO-)(hypochlorite ions) + H3O-
- Group 2 Elements
- It has 2 electrons in its outer shell
- REDOX reactions are most common
- Group 2 Elements
- It has 2 electrons in its outer shell
- REDOX reactions are most common
- Redox with OXYGEN to form METAL OXIDE
- Redox With WATER to form ALKALINE HYDROXIDE
- Redox with DILUTE ACID to form a SALT & HYDROGEN GAS
- REDOX reactions are most common
- It is a REDUCING AGENT - It reduces another species whilst itself gets oxidised
- Trends: As you go down the group (IE decreases, atomic radius increases and shielding increases so)They get MORE REACTIVE and STRONGER REDUCING agents
- Uses
- Agricultural- CaOH is added to neutralise acidic soil
- Bases- G2 Carbonates, Oxides and Hydroxides have many uses as bases due to properties
- G2 Bases are used as Antacids to neutralise HCl stomach acid- Many tablets contain MgOH , CaCO , & MgCO
- It has 2 electrons in its outer shell
- Redox with OXYGEN to form METAL OXIDE
- Redox With WATER to form ALKALINE HYDROXIDE
- Redox with DILUTE ACID to form a SALT & HYDROGEN GAS
- Group 2 Elements
- REDOX reactions are most common
- It is a REDUCING AGENT - It reduces another species whilst itself gets oxidised
- Trends: As you go down the group (IE decreases, atomic radius increases and shielding increases so)They get MORE REACTIVE and STRONGER REDUCING agents
- Uses
- Agricultural- CaOH is added to neutralise acidic soil
- Bases- G2 Carbonates, Oxides and Hydroxides have many uses as bases due to properties
- G2 Bases are used as Antacids to neutralise HCl stomach acid- Many tablets contain MgOH , CaCO , & MgCO
- It has 2 electrons in its outer shell
- Mendeleve:
- Add one spatula of each G2 METL OXIDE to Water in a test tube, SHAKE the mixture ( there isn't enough water to dissolve all of the metal oxide so a WHITE PRECIPITATE forms), Measure the pH of the sample, ALKALINITY INCREASES DOWN A GROUP
- Solubility test
- Solubility test
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