BIO 203 Lecture 2: bio 203 chapter 2

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Chapter 2 Lecture week 2
Chemistry Comes to Life
Outline
The nature of atoms
Chemical bonds and compounds
The role of water in life
Major molecules of life
The Nature of Atoms
-Everything that takes up space and has mass is called matter
- All matter is made of atoms, each containing a nucleus with protons and neutrons surrounded
by a cloud of electrons
Element
An element is a form of matter that can't be broken down into simpler substances
Made up of many atoms that are all the same
Examples: gold, iron, oxygen
-Each element has an atomic number and atomic mass
Atomic number: the number of protons in the nucleus
Atomic mass: the number of protons plus the number of neutrons, as electrons have an
insignificant mass
-Elements with the same number of protons but different numbers of neutrons are called
isotopes
Example of carbon atom
All carbon atoms have six protons in the nucleus
Chemical Bonds and Compounds
-two or more elements may combine to form a compound
-a compounds characteristics are usually different from those of the individual elements
- the atoms in a compound are held together by chemical bonds.
Covalent Bonds: form when 2 or more atoms share electrons
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