BIOL 1500 Chapter Notes - Chapter 2: Electron Shell, Atomic Number

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8 Feb 2013

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BIOL 1500
Everything is made up atoms.
The chemistry that is the most important in biology revolves around a few important
Whatever the element, if you keep cutting it into ever smaller pieces, each of the pieces
behaves exactly the same as any other piece
Everything around us, living or not living can be reduced to atoms
o At the centre of an atom is the nucleus, usually made up of two types of particles
called protons and neutrons.
o Protons are particles that have a positive electrical charge
o Neutrons are particles that have no electrical charge
o The amount of matter in a proton or neutron, its mass is about the same.
o An electron weighs almost nothing. Whirling around the nucleus of every atom are
negatively charged particles called electrons
Particles that have the same charge repel each other, those with opposite charges are
attracted to each other
So far 90 elements have been discovered that are present in nature, and 25 can be made in
a laboratory
The number of protons in an atom’s nucleus determines what element it is (atomic
o The number of neutrons is usually equal to the number of protons
o The mass of the atom is about double its atomic number
Four elements make up more than 96% of your body
o Oxygen (65%), carbon (18.5%), hydrogen (9.5%), and nitrogen (3%)
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