Origin of Elements

• Living cells and organisms consist of elements arranged into recognizable structures

Origin of Elements

• Elements are thought to have been formed through the Big Bang, fusion reactions in stars, and artificial synthesis

• The Big Bang is the explosion of a hot, dense ball of matter which created hydrogen and helium

• Gravitational forces brought gas clouds together, leading to galaxies with billions of stars

• Elements besides hydrogen and helium were created in the center of the stars, and released when some of those stars exploded

• Temperatures and reactant concentrations needed for element formation are achieved in star cores

• High temperatures are needed to overcome electrostatic repulsion between positively charged nuclei for fusion

• Fusion reactions radiate heat and light, this creates a star from gas clouds

• Enormous energy release can lead to the star's explosion

• Most visible stars generate light by burning hydrogen into helium

• Hydrogen that fuels stars is used up, and exhausted more rapidly in larger stars like the sun

• When hydrogen is exhausted, the core temperature reduces and the star starts to collapse

• Heat from collapse increases the temperature to levels to ignite helium

• Two helium nuclei fuse to form beryllium (8Be), however, it is unstable, and does not survive for long

• A helium nucleus fuses with beryllium to form carbon-12

• Additional fusion with helium forms oxygen-16

• The largest atom formable from nuclear fusion is iron (Fe)

• Atoms larger than iron are formed when neutrons explode from the star and are captured by iron nuclei

• Even-numbered elements are more abundant than odd-numbered ones

• The relative abundance of elements is related to the formation mechanism and stability of the formed nuclei

Laboratory Synthesis

• Elements with an atomic number greater than 92, called transuranium elements, have been synthesized
• High-energy particles are produced in cyclotrons that are required to use with target nuclei
• The synthetic element Californium can be formed by using a cyclotron to accelerate carbon-12, and fuse with uranium-238

Elemental Composition of Cells

• There are over 117 elements, but less than a third are found in cells through natural selection
• The percentage of atoms located on the earth are:
  • Oxygen (48.86%)
  • Iron (18.84%)
  • Silicon (13.96%)
  • Magnesium (12.42%)
• The percentage of carbon is about 0.10
• There is similarity in the concentration of main ions in seawater and blood plasma
  • Ions like Cu2+, Mg2+, Ca2+, Na+, K+
• Almost every group on the periodic table is represented in living cells

Bulk/Trace Elements Composition

• Major/Bulk elements found in organic compounds of the cell, abbreviated as CHONPS include:
  • Carbon
  • Hydrogen
  • Oxygen
  • Nitrogen
  • Phosphorus
  • Sulfur
• Minor/Trace elements found in fluids that bathe the cell include:
  • Na
  • K
  • Mg
  • Ca
  • B
  • V
  • Mn
  • Fe
  • Co
  • Ni
  • Cu
  • Zn
  • Si
  • Se
  • Cl
  • Br
  • Cr

Key Features

• Majority of major elements are p-block elements
• Major elements form covalent bonds
• Major elements are generally non-metals
• Major elements have smaller atomic sizes/numbers
• Major elements are neither too reactive, nor inert

The Unique Ability of Carbon

• Carbon forms stable covalent bonds
• Carbon is tetravalent
• Carbon has the power of catenation, the ability to form chains
• Carbon forms multiple bonds with itself or other atoms

Other Elements with Three or More Bonds

• Silicon belongs to group IVA, so it is tetravalent

• Silicon has a larger atomic size that causes silicon-silicon bonds to be weak because the atoms cannot approach to overlap effectively

• Silicon-oxygen bonds are very stable whose chains of alternating silicon and oxygen atoms are inert

• Silicon is 140 times more abundant than Carbon, but carbon is preferentially incorporated in living cells

• Nitrogen has five valence electrons, forming nitrogen-nitrogen bond. The bond energy will be low relative to carbon-carbon bonds

• When nitrogen-nitrogen bonds form, there remains a lone pair of electrons on the atoms

• Repulsion between lone pairs on bonded nitrogen atoms will reduce the bond energy of the nitrogen-nitrogen bond

• Chains of nitrogen atoms are expected to be very unstable

• Boron has three valence electrons

• Boron forms electron deficient compounds

• Formation limits the stability of boron compounds

Reasons for Non-Incorporation

• Artificial elements

• Inert elements

• Toxic elements

• Radioactive elements

• Some elements are non-essential for life, but are still valuable in quality of life

  • Lithium compounds like Li₂CO₃ for schizophrenic conditions
  • Platinum and gold complexes are anticancer and anti-arthritis preparations
  • Kaolin contains aluminium and has anti-diarrheal properties