Transcript Ch 8 Matter Part 2

Chapter 8
Earth Chemistry
Part 2
8.1 – Atomic Number
 An
atom of a specific element is different
from other elements by the number of
protons it has
 Atomic Number is the number of protons
in an atom.
 All atoms of any element have exactly the
same number of protons
8.1 – Atomic Number
 The
number of protons also equals the
number of electrons in a neutral atom
 So, the atomic number tells us how many
protons which equals how many electrons
 Example: Oxygen’s atomic number is 8
 It has 8 protons and 8 electrons
8.1 – Periodic Table
 The
periodic table is a list of all the known
elements in order by their atomic numbers
 It is used to classify the elements into
groups
8.1 – Mass Number
 Each
atom has a mass number.
 Mass number is the number of protons
plus the number of neutrons in the atom
 The mass number is not on the periodic
table
8.1 – Mass Number
 You
can use the atomic number and mass
number to find the total number of protons,
neutrons, and electrons
 Mass # - Atomic # = # Neutrons
8.1 – Isotopes
 Atoms
of the same element but with
different numbers of neutrons are called
isotopes
 The more neutrons an atom has the more
mass it has