Download Atomic Notation

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Atomic Information
 All atoms are composed of the same basic particles, yet not all
atoms are exactly the same. Atoms of
 The atomic number of an element
in the nucleus of that element. Atoms of the same element have
the same number of protons.
 Protons have a positive charge. Electrons have a negative charge.
Atoms are
in nature, which means that the
number of protons equals the number of electrons.
 If electrons are added or taken away, the ratio between protons
and electrons becomes imbalanced and the
Ions
 If electrons are added to the atom, then there are
charges than positive charges. The atom becomes
negatively charged and is called an
.
 If electrons are removed from the atom, then there are
than positive charges. The atom becomes
positively charged and is called a
 The size of the charge is easily calculated. Net charge equals
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Atomic Information
 When an atom has a charge, it is written on the upper right-hand
corner of the element symbol.
o Calcium ion has 20 p+ and 18 e Charge is

Symbol is
o Bromine ion has 35 p+ and 36 e Charge is
 Symbol is
The Neutron
 Early models of the atom only considered two particles of the
atom, the proton and the electron.
 The neutron has a mass about equal to the proton, but has no
charge. Having neutrons would not pose a problem if all atoms of
a particular element had the same number of neutrons – but this is
not the case!
 The number of neutrons can vary.
Isotopes
 Isotopes are atoms of the
.
 The mass number is the
in the nucleus. The mass number is useful
when designating isotopes.
 To write an isotopic symbol, the mass number goes on the top lefthand corner of the element symbol. The number of protons
(atomic number) goes on the bottom left-hand corner of the
element symbol.
o Oxygen – 17
 Means that the mass number is 17. Oxygen has 8
protons, which means that there are 9 neutrons.

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Atomic Information
o Magnesium – 23
 Means that the mass number is 23. Magnesium has 12
protons, which means that there are 11 neutrons.

Atomic Notation
 Example:
 Number of Protons
 Number of Electrons
 Number of Neutrons
Neutrons = Mass Number – Protons
_______ = 37
17