Download Chapter 2: Chemistry of Life

Chapter 2: Chemistry
of Life
2.1 Composition of Matter
• Matter – anything that occupies space and
has mass
• Mass – the quantity of matter an object
has
**Mass vs. Weight**
2.1 Composition of Matter
Atoms
•Atom – the fundamental unit of matter
•Components –
– Nucleus – central core, most of the mass,
consists of proton and neutron
– Proton – positive electrical charge
– Neutron – no electrical charge
– Electrons – negative electrical charge (move
around outside of the nucleus)
– Overall charge of atom = 0 (protons and
electrons cancel each other out)
2.1 Composition of Matter
2.1 Composition of Matter
Elements
•Elements – substances that cannot be broken
down chemically
– Atomic number = # of protons in an atom
– Example – carbon – each atom of carbon has 6
protons so the atomic # is 6
•Isotopes – atoms of the same element that
differ in the number of neutrons
– Mass number – sum of protons and neutrons in
an atom
– Example -
2.1 Composition of Matter
• Radioisotopes – isotopes in which the
nucleus is unstable and tends to release
particles or radiant energy or both
– Can help determine age of fossils
– Can help trace movement of chemicals
through organisms
2.1 Composition of Matter
Compounds
•Compounds – consist of atoms of 2 or more
elements that are joined by a chemical bond
– Compounds often times have different
properties than the elements within the
compound had when by themselves:
Sodium
Chlorine
Sodium Chloride
2.1 Composition of Matter
Two Bond Types
•Ionic Bonds – electrons move from one
atom to another to form a bond
– Example – table salt – NaCl – sodium loses
and electron and chlorine gains an electron
–
–
+
Transfer of
electron
Na
Cl
Na
Sodium atom
Cl
Chlorine atom
Na
Na+
Sodium ion
–
Cl
Cl–
Chloride ion
Sodium chloride (NaCl)
2.1 Composition of Matter
• Covalent Bonds – electrons are shard one
or more pairs of electrons
– Example – methane – CH4 – electrons are
shared in the outer electron shell: