Transcript Chapter 2: The Chemistry of Life

Chapter 2: The Chemistry of Life
Section 2-1: Introduction of
Chemistry
Section Objective
Explain concepts about the structure
and properties of matter
3.4.10A
What is an atom?
An atom is very small!
Consists of:

Nucleus – center of the atom
Protons (p+): subatomic particles with a
positive (+) charge.
Neutrons (no): subatomic particles with no
charge – neutral.
Both have about the same mass = 1 atomic
mass unit (1 amu)
What is an atom?
Consists of: (cont.)

Electron Cloud – outside the nucleus.
Electrons (e-): subatomic particles with a
negative (-) charge.
Electrons move in pathways called
orbitals or shells.
Mass of an electron is negligible.
What is an atom?
Key difference between
atoms of different
elements is the number
of protons and electrons
they contain.
Atoms have equal
numbers of protons and
electrons, so atoms are
electrically neutral.
Opposites Attract
The (+) charge of the nucleus attracts
and holds the negatively charged
electrons in their orbitals.
What is an element?
A chemical element is a substance that cannot be
broken down into any other substance.
The smallest unit of of a chemical element is a
particle called the atom.
What is an element?
96 naturally
occurring
elements.
20 elements have
been artificially
produced in labs.
116 elements total
to date