Bell Work

• Write the electron configuration for an element with an atomic number of 23. Then, draw the electrons in their proper orbitals.

Physical Science – Lecture 38

Introduction to Bonding

Valence Electrons

• 1A = 1 valence electron• 2A = 2 valence electrons• 3A = 3 valence electrons• 4A = 4 valence electrons• 5A = 5 valence electrons• 6A = 6 valence electrons• 7A = 7 valence electrons• 8A = 8 valence electrons

Electron Dot Structures

• Indicates the number of electrons surrounding an element in the outer energy level.

• Represents valence shell electrons

Valence Electrons

• Equal to the group number• Represents electrons in the outer energy level• Elements want valence electrons equal to

noble gases (group 8A)

Octet Rule

• All elements want 8 electrons in their outer shell.

• They want 8 valence electrons to be complete.

• Only exception – Hydrogen and Helium only want 2.

Becoming a Noble Gas

• Elements can lose or gain electrons to become “noble like”.

• Loss of electrons = cation (+ charge)• Gain of electrons = anion (- charge)

• How do we remember each one?

Cations

• Elements lose electrons to become positive• Positive charge comes from an abundance of

protons.• For every electron lost, elements becomes +1.

Example

• If 2 electrons are lost, element becomes +2.

• Mg → Mg2+ + 2e-

Anions

• Elements gain electrons to become negative• Negative charge comes from an abundance of

electrons.• For every electron gained, elements becomes

-1.

Example

• If 3 electrons are gained, element becomes -3.

• N + 3e- → N3-

1+ Cations

• H+ Hydrogen • Li+ Lithium • Na+ Sodium • K+ Potassium• Ag+ Silver • NH4

+ Ammonium• Also, all group 1 elements

+2 Cations• Mg2+ Magnesium • Ca2+ Calcium • Ba2+ Barium • Sn2+ Tin(II) • Pb2+ Lead(II) • Mn2+ Manganese(II) • Fe2+ Iron(II) or ferrous • Hg2

2+ Mercury (I) or mercurous • Co2+ Cobalt(II) • Ni2+ Nickel(II) • Cu2+ Copper(II) • Zn2+ Zinc • Hg2+ Mercury(II) or mercuric • Also all group 2 elements.

+3 Cations

• Al3+ Aluminum • Cr3+ Chromium(III) • Fe3+ Iron(III) or ferric• Also all group 3 elements.

-1 Anions

• F- Fluoride • Cl- Chloride • Br- Bromide • I- Iodide • OH- Hydroxide • CN- Cyanide • NO3

- Nitrate

• NO2- Nitrite

• MnO4- Permanganate

• Also all group 7 elements.

-2 Anions

• O2- Oxide • S2- Sulfide • SO3

2- Sulfite

• SO4 2- Sulfate

• CO3 2- Carbonate

• CrO4 2- Chromate

• Cr2O7 2- Dichromate

• Also all group 6 elements.

-3 Anions

• PO43- Phosphate

• Also all group 5 elements.

Forming Cations/Anions

• Group 1 (1A) = forms +1 Cations• Group 2 (2A) = forms +2 Cations• Group 13 (3A) = forms +3 Cations• Group 14 (4A) = forms +4 Cations or -4 Anions• Group 15 (5A) = forms -3 Anions• Group 16 (6A) = forms -2 Anions• Group 17 (7A) = forms -1 Anions• Group 18 (8A) = Already Noble-like

Why is this useful?

BONDING!

How to Bond.

• Elements can share or take/receive electrons to make them have 8 outer electrons.

Two types of Bonding

• Covalent – between two non-metals. They share electrons.

• A metal will give its electrons to a non-metal to have a completed octet in the octet below its valence shell (becoming a cation).

• A non-metal will take electrons from a metal to fulfill its outer valence shell (becoming an anion).

• Ionic – between a metal and a non-metal or a cation and an anion. They steal or give away electrons to each other.

• Two non-metals will share electrons to make them both think that they have a full outer shell.

Ionic Example

Bonding

Covalent Example

Covalent Bonding

• Must designate through the name how many of each compound are present (since there are no charges to cancel out).

Example – Carbon dioxide

Forming Ionic Compounds

• Ionic compounds come from ions.• The charges cancel out

Compounds

• Form together in whole number ratios

• Formula unit = lowest whole number ratio

Practice

• Can Mg and F form a compound?

• What will this compound look like?

• How many valence electrons are in Mg?

• What is it’s charge when it becomes noble like?

• What is the electron dot structure?

• How many valence electrons are in F?

• What is it’s charge when it becomes noble like?

• What is the electron dot structure?

• How many of each do we need to balance the charges?

• What will the new electron dot structure look like when they bond?

Electron dot structure of Mg and F

Writing Chemical Formulas

• Cation always goes first• Anion always goes last• Numbers of each written as subscripts

Chemical Formula of Mg and F