Bell Work Write the electron configuration for an element with an atomic number of 23. Then, draw...
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Transcript of Bell Work Write the electron configuration for an element with an atomic number of 23. Then, draw...
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