Ch. 2 Warm-UpCh. 2 Warm-Up1.1. What is the difference between an What is the difference between an

atom, element and compound?atom, element and compound?

2.2. What are the 3 main components of What are the 3 main components of an atom? What are their charges?an atom? What are their charges?

3.3. What type of bond is found in:What type of bond is found in: HH22O?O? KCl?KCl? CC66HH1212OO66?? NN22?? Ba(OH)Ba(OH)22 ? ?

Chapter 2Chapter 2

The Chemical Context The Chemical Context of Lifeof Life

Ants & the Ants & the DuroiaDuroia Trees Trees

Ants use formic acid to prevent other plants from growing so that the Duroia trees can serve as their home.

You Must KnowYou Must Know

• The three subatomic particles and The three subatomic particles and their significance.their significance.

• The types of bonds, how they form, The types of bonds, how they form, and their relative strengths.and their relative strengths.

I. Matter vs. EnergyI. Matter vs. Energy

MatterMatter Has mass & Has mass &

takes up spacetakes up space Affected by Affected by

gravitygravity Consists of Consists of

elements and elements and compoundscompounds

EnergyEnergy Moves matterMoves matter Potential, Potential,

kinetickinetic Ability to do Ability to do

workwork ConversionsConversions Sound, light, Sound, light,

heatheat

ElementElement ““purepure”” substance substance Can’t be broken Can’t be broken

down by down by ““ordinaryordinary”” means to another means to another substancesubstance

Ex. hydrogen (H), Ex. hydrogen (H), nitrogen (N)nitrogen (N)

CompoundCompound 2 or more 2 or more

different different elements elements combined in a combined in a fixed ratiofixed ratio

Ex. HEx. H22O, COO, CO22

Elements of LifeElements of Life

• 25 elements25 elements• 96% : O, C, H, N96% : O, C, H, N• ~ 4% : P, S, Ca, K & trace ~ 4% : P, S, Ca, K & trace

elements (ex: Fe, I)elements (ex: Fe, I)

Hint: Remember Hint: Remember CHNOPSCHNOPS

II. Atomic StructureII. Atomic Structure• AtomAtom = smallest unit of = smallest unit of

matter that retains matter that retains properties of an elementproperties of an element

• Subatomic particlesSubatomic particles::

MassMass(dalton or (dalton or

AMU)AMU)

LocationLocation ChargChargee

neutronneutron 11 nucleusnucleus 00

protonproton 11 nucleusnucleus +1+1

electronelectron negligiblenegligible shellshell -1-1

symbol4

2 HeAtomic # (protons or electrons)

Mass # (protons + neutrons)

IsotopesIsotopes # # neutronsneutrons varies, but same # of varies, but same # of

protonsprotons Radioactive isotopes used as tracers Radioactive isotopes used as tracers

(follow molecules, medical diagnosis)(follow molecules, medical diagnosis) Uncontrolled exposure causes harmUncontrolled exposure causes harm

III. Chemical BondsIII. Chemical BondsStrongest Bonds:Strongest Bonds:

1.1. CovalentCovalent: sharing of e: sharing of e--

PolarPolar: covalent bond between atoms : covalent bond between atoms that differ in electronegativitythat differ in electronegativity

NonpolarNonpolar: e: e-- shared equally; eg. O shared equally; eg. O22 or or HH22

III. Chemical BondsIII. Chemical BondsStrongest Bonds:Strongest Bonds:

2.2. IonicIonic: 2 ions (+/-) bond : 2 ions (+/-) bond (givers/takers)(givers/takers)

NaNa++ClCl-- Affected by environment (eg. Affected by environment (eg.

water)water)

Weaker Bonds:Weaker Bonds:

3.3. HydrogenHydrogen: H of polar covalent : H of polar covalent molecule bonds to molecule bonds to electronegative atom of other electronegative atom of other polar covalent moleculespolar covalent molecules

Weaker Bonds:Weaker Bonds:

4.4. Van der Waals InteractionsVan der Waals Interactions: : slight, fleeting attractions slight, fleeting attractions between atoms and molecules between atoms and molecules close togetherclose together

Weakest bondWeakest bond Eg. gecko toe hairs + wall surfaceEg. gecko toe hairs + wall surface

BondsBonds

Covalent Ionic Hydrogen

All important to life

Form cell’s molecules

Quick reactions/ responses

H bonds to other electronegative

atoms

Strong bondWeaker bond (esp. in H2O) Even weaker

Made and broken by chemical reactions

All bonds affect molecule’s All bonds affect molecule’s SHAPESHAPE

affect molecule’s affect molecule’s FUNCTIONFUNCTION

Similar shapes = mimicSimilar shapes = mimic morphine, heroin, opiates morphine, heroin, opiates

mimic endorphin (euphoria, mimic endorphin (euphoria, relieve pain)relieve pain)

Chemical ReactionsChemical Reactions• ReactantsReactants ProductsProducts

• Eg. 6COEg. 6CO22 + 6H + 6H22O O C C66HH1212OO66 + O + O22

• Some reactions are reversible:Some reactions are reversible:• Eg. 3HEg. 3H22 + N + N22 2NH 2NH33

• Chemical equilibriumChemical equilibrium: point at : point at which forward and reverse reactions which forward and reverse reactions offset one another exactlyoffset one another exactly

• Reactions still occurring, but Reactions still occurring, but no net no net changechange in concentrations of in concentrations of reactants/productsreactants/products