life depends on chemistry!. the big bang theory accepted scientific theory to explain what happened...
TRANSCRIPT
Life Depends on Chemistry!
The Big Bang Theory
The Big Bang Theory• Accepted scientific theory to explain
what happened at the very beginning of our universe
• Occurred approximately 13.7 BYA
• In the instant after the big bang, the universe expanded with incomprehensible speed from its pebble-size origin to an astronomical scope
• As matter cooled, more diverse kinds of atoms begin to form and eventually condense into the stars and galaxies of our present universe
So, just how big is a billion?
How long would it take you to count to a billion?If it took you 3 seconds to say every number it would take you approximately 98 years!
How long would it take you to earn a billion dollars? (excluding if you are Bill Gates, Mark Zuckerburg, or Oprah of course!)
If you earned:$100/day for 5/wk = $25,000/yr = approx 40,000 years!
$1000/day for 5/wk = $250,000/yr = approx 4,000 years!
What about a billion pieces of paper?
At about 0.1 mm thick, it would stretch approx 62 miles
AtomsAll matter is composed of atoms.
100 million atoms would make a row about 1 cm long, about the width of your pinkie!
Composed of 3 subatomic particles:
Protons (+) chargedElectrons (-) chargedNeutrons (no charge)
Nucleus: center of atom made of protons and neutrons
ElectronsHave a negative (-) charge
Are in constant motion around the nucleus
Electrons orbit in energy (E) levels
1st level holds 2 e-s2nd and 3rd hold 8 e-s# of e-s in the HIGHEST E level determines the chemical properties of an atom
Elements and CompoundsElement: a substance made up of one kind
of atom Ex: Hydrogen, Carbon, Fluorine
Compound: substance formed by 2 or more elements
Ex: H2O (water), CO2 (carbon dioxide), C6H12O6 (sugar)
IsotopesAtoms of the same element that differ in their # of NEUTRONS
Elements ALWAYS have the same number of protons and electrons -> same chemical properties
Atomic Number– The # of + found in the nucleus
– The # of + = the # of -– Periodic Table is arranged by
this number Symbol
– “Shorthand” for the element – Note 2nd letter is always lowercase
Atomic Mass Number – Total AVERAGE mass of Protons
+ Neutrons
17
Cl
35.5
Electron Configuration
Let’s practice!
Hydrogen (atomic # = 1)
Electron Configuration
Helium (atomic # = 2)
Electron Configuration
Oxygen (atomic # = 8)
Oxidation Reactions and Oxidation Numbers
An oxidation-reduction reaction is any chemical rxn where the oxidation number of a molecule, atom, or ion changes by gaining or losing an electron
Oxidation # indicates the charge on the atom (or ion) when electrons are lost, gained, or shared in chemical bonds
Oxidation is Lost Reduction is Gain
Deciphering the Periodic Table
Oxidation NumbersOn the periodic table:
Strong electron donors are on the LEFT side
(+ )O.N. indicate element will lose/donate an e-
Strong electron acceptors are on the RIGHT side
(-) O.N. indicate that the element will gain/accept an e-
The further apart two elements are on the periodic table, the more likely they are to form an ionic compound
Electron Configuration
What would be the electron configuration for Sodium (Na)? Atomic # = 11
What would be the electron configuration for Chlorine (Cl)? Atomic # = 17
How would you change your drawing of Na to give it a charge of positive 1? (Na+ ion)
How would you change your drawing of Cl to give it a charge of negative 1? (Cl- ion)
Oxidation NumbersA sodium atom always ionizes to become Na+ (a charge of +1) when it combines with other atoms to make a compound.
Sodium has an oxidation number of 1+.What is chlorine’s
oxidation number?
Why does this matter?!
Bonding!Remember our earlier definition of a compound (substance formed by 2 or more elements)
Re-Dox reactions explain the sharing and transferring of electrons in chemical reactions
Crash Course
BondsBonds are formed using valence electrons
Valence electrons: e- in the outer shell of an atomIn bonds, the valence e- are shared or transferred btn atoms
Covalent BondsThe sharing of electrons between atoms
Occurs between two atoms of the same element or of elements close to each other in the periodic table
In this example, a phosphorous atom is sharing its 3 unpaired electrons with 3 chlorine atoms. In the end, all 4 of these molecules have 8 valence electrons, satisfying the octet rule
Ionic BondsThe complete transfer of valence electrons between atoms
Generates two oppositely charged ions
In this example, the sodium atom is donating its 1 valence electron to the chlorine atom. Notice, the net charge of the resulting compound is 0.
Polar CovalentExample: H2O (a polar MOLECULE)
Polar indicates that there is an uneven charge O is an e- TAKER, it needs 2 more to fill its outer shellH is an e- GIVER
Unlike Na, it doesn’t just release its e- quite so easily b/c it only has ONE electron
The electrons being shared by the atoms spend a greater amount of time, closer to the Oxygen nucleus than the Hydrogen nucleus.
This results is an unequal electron association where one part of the molecule (O) has a – charge and the (H) has a + charge
Hydrogen BondsWhen water molecules are close together, their + and – regions are attracted to the oppositely charged regions of nearby molecules
Van der Waals ForceRelatively weak, temporary,
intermolecular force that holds molecules together
Occur between molecules b/c negatively charged electrons move to create slightly different charges from one end of the molecule to the other
GeckosRead How Geckos Stick on der Waals
In your notebook, copy and respond to the following questions:
How are geckos able to stick to walls?Describe how scientists deduced which of the two proposed hypothesis were true.
TED Ed: How do Geckos defy gravity?