Learning Objectives

Describe the formation of ions by electron loss/gain in order to obtain the electronic configuration of a noble gas.

What are ions?

Ions are formed when atoms gain or lose electrons.

Why do atoms form ions???

Question

3

Characteristics

• Belong to Group 18 of the periodic table.
• Stable and unreactive
• Exist as single atoms

4

5

Why are noble gases

unreactive?

6

What do you notice about the
valence shell?

2 2,8 2,8,8 2,8,8,8 2,8,8,8,8

6

What do you notice about the
valence shell?

2 2,8 2,8,8 2,8,8,8 2,8,8,8,8

Ans: They have a full valence shell
🡪 noble gas configuration

7

How about other elements?

2,1

2,5

​2,2

​2,3

​2,4

​2,6

​2,7

7

How about other elements?

​Sadly, they do not have a full valence shell...

So how can other elements become like noble gases?

8

They form ions by gaining or losing electrons

They form ions by gaining or losing electrons

in order to achieve noble gas configuration.

10

Ions

• An ion is an atom that has gained or lost an electron or electrons.

• An atom that loses an electron or electrons will have more protons than electrons, it will become an ion with a positive charge.

• An atom that gains an electron or electrons will have more electrons than protons, it will become an ion with a negative charge.

• Atoms that have a charge can only gain or lose electrons they cannot gain or lose protons.

Cations and Anions

• Cations- pronounced cat-ion- is an ion with a positive (+) charge (it will be an ion that lost electrons). It has more protons than electrons.

• Anions- pronounced an-ion- is an ion with a negative (-) charge (it will be an ion that gained electrons). It has more electrons than protons.

Valence Electrons and Ions

• Atoms gain or lose electrons from the highest energy level.

• The atoms in the highest energy level are called valence electrons.

• Elements in group 1 like Lithium [Li] have 1 valence electron.

• Elements in group 2 like Berylium [Be] have 2 valence electrons.

• Elements in group 13 like Boron [B] have 3 valence electrons.

• Elements in group 14 like Carbon [C] have 4 valence electrons.

• Elements in group 15 like Nitrogen [N] have 5 valence electrons.

• Elements in group 16 like Oxygen [O] have 6 valence electrons.

• Elements in group 17 like Flourine [F] have 7 valence electrons.

Octet Rule

• The octet rule determines if an atom will gain or lose electrons.

• The outer level of an atom has eight electrons.

• An atom will gain or lose electrons to have a full outer energy level.

• Atoms of metals tend to lose their valence electrons.

• Nonmetals tend to gain or share electrons to achieve a full octet.

Will an atom gain or lose an electron?

• Atoms in group 1, 2, and 13 lose electrons. Remember the atom want a full outer energy level.

• For atoms that lose electrons, they empty the outer most energy level.

• For groups 1, 2 and 13 - atoms lose electrons forming a positive ion.

• For groups 15, 16 and 17 - atoms gain electrons forming a negative ion.

• For group 14- atoms can gain or lose electrons forming a positive or negative ion.

Elements that lose electrons form CATION

• Atoms that lose electrons have more protons than electrons, the ion that forms has a positive charge and is a cation.

• They are part of representative groups 1 , 2 , 13 and 14 in the periodic table.

• For example sodium [Na] atom is in group 1, it will lose 1 electron and will have the +1 charge to make it a sodium ion [Na⁺].

• For example magnesium [Mg] atom is in group 2, it will lose 2 electron and will have the +2 charge to make it a magnesium ion [Mg⁺²].

  CONTINUE COPYING THE EXAMPLES IN THE WHITEBOARD

Elements that gain electrons form ANION

• Nonmetals tend to gain or share electrons forming negative ions or anions.

• When an atom gains an electron or electrons it forms an ion with more electrons than protons. It forms a negative ion (an anion).

• To determine the charge of a negative ion (anion) subtract 8 (to obey with the octet rule)

• Example- Flourine atom is in group 17. Group 17 has 7 valence electrons subtract 8 (to obey with the octet rule) so that would be (7-8= -1) . That makes a Flourine ion [F^-].

CONTINUE COPYING THE EXAMPLES IN THE WHITEBOARD

​Ionic, covalent and metallic bonds