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
Hg22+ 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
•
•
•
•
•
•
•
•
•
•
FFluoride
ClChloride
BrBromide
IIodide
OHHydroxide
CNCyanide
NO3Nitrate
NO2Nitrite
MnO4Permanganate
Also all group 7 elements.
-2 Anions
•
•
•
•
•
•
•
•
O2Oxide
S2Sulfide
SO3 2- Sulfite
SO4 2- Sulfate
CO3 2- Carbonate
CrO4 2- Chromate
Cr2O7 2- Dichromate
Also all group 6 elements.
-3 Anions
• PO43Phosphate
• 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