11 Chem, week 4 - First Test

Hey my loyal followers.  This week is a bit different as I only did my test, so I thought that I'd run through all of the key concepts in the first unit.

Module 1: Introduction

Mr. Aristotle, in all his stone-cold glory

• Popular belief about current science can, in fact, influence the trends which scientific research follows
• Atomic theory!
• John Dalton created atomic theory, theorized about atoms
• J.J. Thomson discovered, identified electron
• Ernest Rutherford thought up the planet model of the atom (the Gold Foil experiment!)
• Neils Bohr one-upped Rutherford and placed the electrons of any given atom within a specific energy level
• The different gas tests
• Hydrogen: lit splint explodes (very small)
• Oxygen: glowing (!!) splint relights
• Carbon dioxide: Lit splint goes out
• Ammonia: same as carbon dioxide but ALSO turns red litmus paper blue
• Chlorine: turns blue litmus paper to red to white
• The list of chemical changes (by now most of this is review)
• Colour change
• Gas is produced (bubbling)
• Precipitate is formed
• Electricity or light is produced
• Heat is given off (exothermic) or taken in (endothermic)
• Sound is produced
• Odor is produced
• OH and the Average Atomic Mass problems!  Those were fun, I liked the math involved.

Module 2: Trends in the Periodic Table

The trends of the periodic table!

• Atomic radius
• Down a group: radius increases (more valence shells)
• Across (left to right) a period: Radius decreases (more protons = more attraction)
• Ionization energy
• Down a group: ionization energy decreases (valence electrons are further away = less attracted to nucleus =  easier to snatch them)
• Across a period: ionization energy increases (valence electrons closer due to radius getting smaller = more attracted to nucleus = harder to snatch them)
• Electron affinity
• Down a group: affinity decreases (electrons added to further valence shells = less of an impact on nucleus)
• Across a period: affinity increases (electrons added to shells that are closer due to radius getting smaller = more of an impact on nucleus)
• Electronegativity (not shown on above graph)
• Down a group: e.n. decreases (valence shells are further from nucleus = potential electrons less attracted to nucleus)
• Across a period: e.n. increases (valence shells are closer to nucleus AS WELL AS halogens would want to gain an electron more than an alkali would b/c it's easier for the alkali to lose an electron than to gain seven)

Module 3/4: Ionic/Covalent Compounds

A very snazzy Bond... Ionic, not James

• Before anything we learned how to draw Lewis dot diagrams (and in the covalent module, simply Lewis diagrams)
• Ionic bonds!
• Created with two or more ions
• Electronegativity comes into play as the nonmetal of the bond will RIP the valence electrons away from the metal and just, kinda... hang out with them.  The resulting ions are then attracted to each other
• Form lattice structures
• And then we learned how to write ionic equations (sigh)
• Covalent Bonds!
• Created through sharing of valence electrons by two or more atoms
• Made with NONMETALS whereas ionic bonds are made of a METAL and a NONMETAL
• Form clumps instead of a lattice structure
• Dissolves into molecules
• WHEN DOING LEWIS DIAGRAMS FOR COVALENT BONDS, the atom with the lowest valence number ALWAYS goes in the CENTER (unless your lowest valence in the equation.  Hydrogen never goes in the center.  Never.  Ever.  You don't want to know what happens when hydrogen gets that kind of political leverage (but seriously hydrogen never goes in the center of a Lewis diagram))

Module 5: Lab Task

Did you mean...

Sodium chloride, MOTHER???????

• Differences between NaCl (ionic bond) and sucrose (covalent bonds)
• NaCl has incredibly high melting point, sucrose does not
• NaCl is partially soluble in water, whereas sucrose is completely soluble
• NaCl is conductive in water, whereas sucrose is not
• NaCl ionizes and breaks apart in water, whereas sucrose molecules stay together
• Ah yes, and then oleic acid got thrown into the mix!  I won't go into much detail here (if you'd like a decently in-depth explanation please ask in the comments) but while oleic acid is also made of covalent bonds, it acts differently in water than sucrose does.  To be specific, oleic acid is not soluble

Module 6: Electronegativity

Man, hydrogen just can't catch a break!

Actual picture of oxygen fighting hydrogen for electrons

• Ideas about electronegativity
• Electronegativity is a relative value
• Differences in bonded atoms' e.n. values causes one atom to hoard the bonded pair of electrons more than the other atom, causing the electrical charges to be distributed unevenly and create a polar covalent bond
• Diatomic molecules, as well as other bonds where the e.n. values of the bonded atoms are almost equal, form non-polar covalent bonds (not electrically charged)
• Extreme e.n. differences (i.e. between a metal and a nonmetal) cause ionic bonding!
• Dipoles!!!!!!!
• A dipole is either 1) the polar bond created by the sharing of electrons between atoms, or 2) the polar molecule itself (created from polar bonds which do not counteract one another)
• Three types of bonds
• Non-polar covalent: Either a) a bond where the e.n. values of the bonding atoms are exactly or nearly identical, or b) a molecule where opposite polar bonds counteract their forces and cancel out (actually, this is an example of a molecule that has dipoles within it but is not itself a dipole)
• Polar covalent: a bond where the e.n. values of the bonding atoms are different
• Ionic: a bond where the e.n. values of the bonding atoms is really different (so different that one atom rips away the electrons of the other atom)

And there you go!  I hope you enjoyed this.  I will be back to my regular template next week.  Thank you for reading!

 - L