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• Proton = + charge• Neutron = neutral charge• Electron = - charge
Ions• Ions are atoms that have lost or gained one or more electrons giving them a positive or negative charge!
For example: Na (Sodium), has originally 11 electrons but when an electron is lost it becomes a postive ion. Na +
If an ion looses an election it has a positive charge.
If an ion gains an electron it has a negative charge.
What causes an atom to become an ion?• When an atom loses or gains one or more
electrons it acquires a net electrical charge called an ion.
• The net charge of an ion is found by subtracting the number of electrons from the number of protons
Charge of Ion = number of protons – number of electrons
A neutral magnesium atom (atomic number=12) has 12 protons/electrons. If it loses 2 electrons it becomes an ion with a charge of 2+.
Number of protons 12Number of electrons - 10 Charge of Ion 2+
19. Cu²+
20. F-
29
9
Ion Protons Electrons
27
10
Isotopes• Isotopes are atoms that have the same
number of protons but different numbers of neutrons
• Most elements in the first two rows of the periodic table have at least 2 isotopes with one being more common than the other
• In nature, elements are almost always found as a mixture of isotopes
Hmm
Hydrogen Deuterium Tritium
•For example, the most common isotope of hydrogen has no neutrons at all
•There's also a hydrogen isotope called deuterium, with one neutron, and another, tritium, with two neutrons.
Neutron
Proton
Isotopes of Hydrogen
Most common isotope
• To identify an isotope more specifically, chemists add a number after the elements name.
ex. Carbon-11 Carbon-12 Carbon-14• This number is called the isotope’s mass number
and is the sum of the isotope’s number of protons and neutrons.
• For example, an atom with 17 protons and 20 neutrons has a mass number of 37.
Q. What is the mass of the Nitrogen isotope with 7 protons and 12 neutrons?
A. Nitrogen-19
iodine-128
potassium-40
53
19
53
19
75
21
Atom Protons Neutrons Electrons
Examples
To name an isotope using chemical symbols
simply place the atom’s mass number to the upper left of the element symbol. For example 37Cl.
#neutrons = atomic mass – atomic number
37 – 17 = 20 neutrons
How many protons, neutrons, and electrons are present?
5626
STEP 1: The atomic number in the lower left corner = 26 protons. The difference between the mass number and the atomic number is 56 – 26 = 30. There are 30 neutrons.
STEP 2: The charge on the ion, 2+ shows us that there are 2 more protons than electrons, indicating that there are 24 electrons.
Fe 2+
Isotope Symbols
141
56
Mass number (M)
Atomic number (Z)
ChargeBa2+
Number of protons = ZNumber of neutrons = M – Zcharge = Z– Number of electrons