Main Group Ions

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The Octet Rule
and Forming Ions

Lab #4 Make compounds

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Table of Contents:

Ionic Compounds and Ionic Bonding

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·The Octet Rule and Forming Ions

·Ionic Bonding

·Ionic Formulas

·Ionic Compounds with Transition Metals

·Polyatomic ions

·Naming Polyatomic Ions

Atoms tend towards having a full outer shell consisting of:

·2 electrons in their outer s-orbital
·6 electrons in their outer p-orbital

That yields an outer electron configuration of ns2p6

Where "n" is the element's highest principal quantum number.

The number "n" is also equal to the period in which the atom is located.

Octet Rule

Atoms tend towards having a total of 8 valence electrons.

This can also be called an octet of valence electrons.

This is why the ideal gases (Group 18) are nonreactive.

They have an outer electron configuration of ns2p6, so they want to
neither gain nor lose electrons.

They are stable.

Octet Rule

Valence Electrons

The number of valence electrons in an atom in the Main Group
(Groups 1, 2, and 13-18) is the last digit in the group number.

·For example, atoms in group 2 have 2 valence electrons.

·Atoms in group 17 have 7 valence electrons.

The number of valence electrons in groups 3 - 12, the transition
metals, can vary and cannot be determined by their Group
Number.

Valence Electrons

Valence electrons are usually the electrons in the outermost s and
p subshells.

Valence electrons determine the chemical properties of an element.

Valence
electron

Objective

• Cations and anions

• How metal and nonmetals bond with different numbers of valence electrons

• What are cations?

• What are anions?

  
  
  

Metals like to donate electron

ex. sodium, Na or Lithium, Li

Having 1 valence electron, it's donated to an atom like halogen, the most reactive non metal

When the electron is donated, what happens to the atom's charge?

Multiple Select

What happens to the metal magnesium that donates 2 valence electrons? Keep in mind, valence electron is an electron with a negative charge.

• The metal becomes a cation

• The metal becomes neutral

• The metal becomes an ion with +2 charge

• The metal becomes an ion with -2 charge

Cation, positive charge ion

Na, sodium has 1 valence electron

Na -> Na+ + 1e-

Mg, magnesium has 2 valence electrons

Mg -> Mg2+ + 2e-

Non-metals like to accept electrons

Ex. chlorine Cl, oxygen O, nitrogen N

Accepting 1 or more electrons, these atoms reach octet, the stable state of the atom

Multiple Select

What becomes of an atom phosphorus, P, when it gains electrons?

How many electrons will it gain?

• It becomes a cation, +3

• The net charge becomes -3

• It becomes neutral

• This non-metal becomes an anion

Valence Electrons

1 2 3 4 5 6 7 8

1 or more

There is one exception:
helium has only 2 valence electrons.

Number of valence
electrons in neutral atoms:

Cations are positive and are
formed by elements on the
left side of the periodic table
(the metals).

Ions

Anions are negative and
are formed by elements on
the right side of the periodic
table (the nonmetals).

Ions are atoms or groups of atoms that have become charged
by either gaining or losing electrons.

The Formation of Cations

Na atom

Na+ ion

loses e-

11p
11e-
11p
10e-

The Na+ ion is smaller than the Na atom since it's outer shell is no
longer occupied.

Group 2 cations
always have a
charge of +2.

The Formation of Cations

1

2

Group 1 cations
always have a
charge of +1.

For example, Mg will
lose two electrons to
become Mg2+.

The Formation of Cations

1

2

For example, Na will
lose one electron to
become Na+.

Mg

Mg2+

2e-

+

Na

Na+

e-+

The + symbol in Na+
indicates 1 unit of
positive charge.

The 2+ symbol in Mg2+
indicates 2 units of
positive charge.

Nonmetals usually gain valence electrons.

The result is a noble gas electron configuration of
8 valence electrons.

The Formation of Anions

Cl: [Ne] s23p5

Cl-: [Ne] 3s23p6

1s

2s

2p

3s

Gain of
valence
electron

3p

1s

2s

2p

3s

3p

The Formation of Anions

Shown below are electron configurations of the chlorine anion Cl-1
side-by-side with the electron configuration of argon (Ar).

They look the same. The difference is that argon is electrically
neutral while the chlorine ion has a charge of -1.

Cl-: [Ne] 3s23p6

1s

2s

2p

3s

3p

1s

2s

2p

3s

3p

Argon atom [Ar]

The Formation of Anions

Cl atom

Cl- ion

Gains an e-
17P

17e-
17p

18e-

The Cl- ion is larger than the Cl atom since it has an additional
valence electron.

The Formation of Anions

15 16

17
Group 15 anions always have a charge of 3-

Group 16 anions always have a charge of 2-

Group 17 anions always have a charge of 1-

Multiple Choice

1 How many valence electrons does potassium have?

• 3

• 1

• 19

• 4

Multiple Choice

2 How many valence electrons does Aluminum have?

• 5

• 3

• 7

• 27

Multiple Choice

3 How many valence electrons does Barium have?

• 1

• 2

• 52

• 3

Multiple Choice

4 Metals tend to __________ electrons and nonmetals tend to __________ electrons.

• gain, gain

• lose, lose

• gain, lose

• lose, gain

Multiple Choice

5 Anions tend to be __________ and cations tend to be __________.

• metals, metals

• metals, non metals

• nonmetals, metals

• metals, nonmetals

Multiple Choice

6 This is the ion formed from a calcium atom.

• Ca+

• Ca-

• Ca+2

• Ca-2

Multiple Choice

7 Phosphorous forms an ion with a charge of __________.

• 3-

• 3+

• 2+

• 5-

Multiple Choice

8 Aluminum forms an ion with a charge of __________.

• 2+

• 2-

• 3+

• 3-

Multiple Choice

9 Of the following, __________ contains the greatest number of electrons.

• P3+

• P

• P-2

• P-3

Multiple Choice

10 Oxygen forms an ion with a charge of __________.

• 2-

• 2+

• 3-

• 3+

Multiple Choice

11 Iodine forms an ion with a charge of __________.

• 7-

• 2-

• 2+

• 1-

Multiple Choice

12 This is the ion formed from nitrogen.

• N2+

• N3+

• N3-

• N5-

Multiple Choice

13 Predict the charge of the most stable ion of S.

• 2+

• 2-

• 3+

• 3-

Multiple Choice

14 What would be the expected charge on the gallium (Ga) ion?

• 2+

• 3+

• 4+

• 3_