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 → Mg e -

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 - → N 3-

1+ Cations H + Hydrogen Li + Lithium Na + Sodium K + Potassium Ag + Silver NH 4 + Ammonium Also, all group 1 elements

+2 Cations Mg 2+ Magnesium Ca 2+ Calcium Ba 2+ Barium Sn 2+ Tin(II) Pb 2+ Lead(II) Mn 2+ Manganese(II) Fe 2+ Iron(II) or ferrous Hg 2 2+ Mercury (I) or mercurous Co 2+ Cobalt(II) Ni 2+ Nickel(II) Cu 2+ Copper(II) Zn 2+ Zinc Hg 2+ Mercury(II) or mercuric Also all group 2 elements.

+3 Cations Al 3+ Aluminum Cr 3+ Chromium(III) Fe 3+ Iron(III) or ferric Also all group 3 elements.

-1 Anions F - Fluoride Cl - Chloride Br - Bromide I - Iodide OH - Hydroxide CN - Cyanide NO 3 - Nitrate NO 2 - Nitrite MnO 4 - Permanganate Also all group 7 elements.

-2 Anions O 2- Oxide S 2- Sulfide SO 3 2- Sulfite SO 4 2- Sulfate CO 3 2- Carbonate CrO 4 2- Chromate Cr 2 O 7 2- Dichromate Also all group 6 elements.

-3 Anions PO 4 3- 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