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?