• 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