chemistry unit 1

• What is oxidation?


  The loss of electrons
• What is reduction?

  The gain of electrons
• If something has been reduced, what is it?

  Oxidising agent (it has gained electrons, causing a different species to lose electrons)
• If something has been oxidised, what is it?


  Reducing agent (it has lost electrons, causing a different species to gain electrons)
• How do metals react in terms of electrons?

  React by losing electrons- oxidised- reducing agent
• How to non-metals react?

  React by gaining electrons- reduced- oxidising agent
• What are the rules for oxidation state numbers?

  F is always -1O is always -2 H is always +1
• What are the exceptions of the rules of oxidation numbers?

  Hydrogen peroxide (oxygen in -1)Lithium hydride (hydrogen is -1)
• What has happened if the oxidation number decreases?

  It has been reduced so is an oxidising agent
• What has happened if the oxidation number has increased?

  It has been oxidised so is a reducing agent
• Atomic Number


  No. of protons in the nucleus
• Mass Number

  No. of protons + no. of neutron
• Isotopes

  Atoms which have the same number of proton, but a different number of neutrons
• Exam Tips

  Atomic Number = Number of protonsNumber of protons = Number of electronsNumber of neutrons = Mass no. - Atomic no.
• Representing atoms key positions

  
• Radioactivity

  Isotopes are unstable and split up to form smaller atoms. The nucleus divides, causing protons, neutrons and electrons to fly out.
• Types of emmission

  Alpha, Beta and gamma are types of radiation given off from unstable isotopes.
• Alpha Particles

  Consist of two protons and neutrons and are helium nuclei. Least penetrating and are stopped by paper or even air. Highly ionising.
• Beta Particles

  Consists of streams of high energy electrons and are more penetrating. Stopped by 5mm of aluminium. weak ionising.Beta particles are electrons from nucleus not electrons
• Gamma Particles

  High energy electromagnetic waves and most penetrating, pass through many centre metres of lead. Least ionising to none.
• Alpha Emission

  Mass number decrease by 4 and the atomic number by 2

  
• Beta Emission

  Mass number stays the same and atomic number gains 1

  
• Beta Decay


  Normal: moves one place to the right in periodic tableElectron: Opposite: Atomic number loses 1, as a positively charged electron i used. (positron) One place to the left.
• Gamma Emissions

  No change
• Radiation on living cells

  Everyone receives background radiation, but it isn't harmful unless it taken in by big doses. High level radiation causes serious damage to cells and organs
• Radiodating

  Half life can be used to determine the age of either organisms or rocks. Carbon-12 is used to measure.
• Radiation in medicine

  Cobalt-14 is used in radiotherapy for the treatment of cancer. High energy is used to kill cancer cells.
• Radiation in industry and analysis

  Beta is used to measure the thickness of metal sheets
• Half Life


  The time taken for half of the nuclei to decay.
• Half life importance


  Indicated how quickly isotopes decayNot effected by the original mass or the temperatureDifferent from one radioisotope to anotherInversely proportional to the rate of decay
• The half life of ¹³³Xe is 5 days. How long does it take 64g of ¹³³Xe to disintegrate to 1g


  64→32→16→8→4→2→1 6*5 = 30 days
• S atomic orbital

  e.g 1s
• P orbital


  Measure at right angels within the shell

  
• Determination of greater ionising ennergy

  Nuclear charge - No. protonsAtomic radius - Distance from electron to nucleusThe shielding effects - Number of full outer shells outer shell and nucleus
• Describe the line emission spectrum of hydrogen.

  A series of dark lines of light of an exact frequency on a black background. The lines get closer together as frequency increases. (Balmer series - visible region - n=2)
• What are the two equations needed when dealing with frequencies and wavelengths etc...?


  Speed of light = frequency x wavelengthC = f x λEnergy = Plancks constant x frenquencyE = h x f
• What happens to wavelength as you increase frequency?

  Decrease wavelength
• What happens to energy as you increase frequency?

  Increase energy
• Explain the line emission spectrum of hydrogen.

  An electrical discharge is passed through atomic hydrogen.An electron in a lower energy level will about an exact amount of energy that is EQUAL to the energy difference between two energy levels.This electron is promoted to a higher energy level.In the higher energy level, the electron is unstable so will fall back into the lower energy level. As the electron falls, it releases energy as an exact frequency of light.This is why we see lines of exact frequency.
• What do the exact lines of light tell us about electrons?

  Electrons can only exist in exact energy levels and these energy levels must get closer together as their energy increases