Elements of life

• Nuclear fission reaction:

  Two light atomic nuclei fuse together to form a single heavier nucleus of a new element.

  this can only happen at high temperatures and/or pressures

  Eg: in stars
• Mass spectrometry:

  measures the atomic (or molecular) mass and abundance of different particles in a sample.

  spectrometer detects ionized atoms.
• Relative atomic mass:

  average Weighed mass of all the atoms of an element compared to 1/12th the mass of a carbon-12 atom.
• Isotope: Atoms of the same element with different numbers of neutrons so different mass numbers.
• Spectroscopy how light and matter interact.

  C = yv

  C= speed of life 3.00 x10^8 ms^-1

  y= wavelength

  v= frequency
• E=hv

  v= energy of photon

  h= planck constant 6.63x10^-34 J^-1
• Bohr’s theory

  when while light is passed through am element (gaseous). Black lines appear in the absorption spectrum.

  the atoms absorbs energy (becomes exited) and the electrons jumps to a higher energy levels.
• Quanta = fixed quantity

  when the electrons drop the lower energy levels they admit Colours
• Orbitals

  the shells are further divided into orbitals. Each orbital can only hold 2 electrons.
• Periodicity

  there is a repeating pattern the melting and boiling points of the elements across periods 2+3

  group 1-4 = general increase in boiling point

  group 4-5 = sharp decrease in boiling point

  group 5-10 = comparatively low boiling point
• Molecular geometry

  simple covalent molecules have a specific 3D shape that can be determined using violence shell electron pair repulsion theory.
• VSEPRT

  electron pairs around a central atom repel to be as far apart as possible; minimises repulsion
• Electrolyte - ionic compounds when molten or in solution
• Ionisation

  the loss of an electron from an atom 1 mole gaseous state
• lone pairs

  pairs of electrons not involved in bonding
• When describing bond angle and shape:

  EG - METHANE

  has 4 regions of electron density around the central atom

  these regions repeals far away as possible/ to minimise repulsion

  giving a bond angle of 109

  a tetrahedral molecular shape
• Ionisation enthalpy

  when are electron is removed from an atom the energy required is called first ionisation enthalpy
• First inonisation enthalypy increases across a period as the number of electrons in the outer shell increases
• Group 2

  all reactive from compounds containing ions with a 2+ charge

  group 2 metals + water -> metal hydroxides + hydrogen
• Group 2 carbonates

  when heated they decompose forming an oxide + CO2

  thermal stability increases down the group.

  MO3 -> MO + CO2
• Basic

  group 2 oxides + hydroxides are basic

  bottom of the group most strong basic
• Standard solution

  Solution with known calculation
• Titration calculations

  C1V1=C2V2
• titration calculation

  1. identify concordent titres
  2. calcuate the mean titre
  3. write a balanced symbol equations
  4. moles = concentration x volume
  5. use equation to determine number of moles
  6. calculate concentration
  7. final anwser with accuracy
• Acid

  a compound that dissociates in water to produce hydrogen ions H+
• Base

  a compound that reacts with an acid to produce water and salt
• alkali

  a base that dissolves in water to produce hydroxide ions

  nuillisation = alkali + acid forms salt and H2O

  salt is always soluble
• Bronsted Lowry theory

  an acid is proton donner

  an base is a proton acceptor

  acids only show their acidc properties when dissolved in water

  a proton is donated to the water molecules by a dative bond and forms the oxanium ion