7 Feb 2019
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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