Bonding

ION Charged atom Na + (has lost one electron) O -2 (has gained two electrons)

Bonding Covalent share electrons Ionic transfer of electrons (lose or gain)

IONIC BOND An atom may lose one or more electrons and become positive (+) An atom may gain one or more electrons and become negative (-) The (+) and (-) ions formed now attract each other and form an ionic bond.

Ionic Bonds Sodium losesChlorine gains an electron become +becomes -

NaCl: Ionic Bond Tutorial 2.1 Chemical Bond Formation

Why do atoms bond? To have filled outer electron shells! Atom Heaven (stable)

Why do atoms bond? See the filled electron shells.

Filled outer e- shells How many e- fill the first shell (nearest the nucleus)? How many e- fill the next two shells? 2,8,8 nucleus

Gain 1 e- or lose 7 e-? If gains 1 e-, then it becomes -1

Gain 7 e- or lose 1 e-? If loses 1 e-, the it becomes +1.

Gain or Lose ? If it could as easily lose or gain e-, then it will probably share them. It will form a covalent bond.

Covalent Bonding = Shared e-

Polar Covalent Bonding of Water: Unequal sharing of electrons

Nonpolar Covalent Bond Equal sharing of electrons Like with carbon dioxide

Bonds Single Bond C-C C:C Double Bond C=C C::C Triple Bond C≡C C:::C

Single Bond and Double Bonds

Chemical Reaction A process to break or share electrons to form or break bonds Click Here Sodium and Chlorine Chemical ReactionSodium and Chlorine Chemical Reaction Also scroll down for covalent bonding AND polar covalent bonding in water

Chemical Reactions Reactants on the left of the arrow Products on the right of the arrow IDENTIFY: 2Mg(s) + O2(g) → 2MgO(s) MgO(s) + H2O(l) → Mg(OH)2(s) N2(g) + 3H2(g) → 2NH3(g)

Chemical Reaction Example A silver spoon tarnishes. The silver reacts with sulfur in the air to make silver sulfide, the black material we call tarnish. 2 Ag + S Ag 2 S

Chemical Reaction Example An iron bar rusts. The iron reacts with oxygen in the air to make rust. 4 Fe + 3 O 2 2 Fe 2 O 3

WATER Polar Covalent Bonds H H O

Polarity of Water Uneven sharing of electrons Polar covalent Polar Bonding

Contrast Polar Uneven distribution of electrons EX: Water Non-polar Even distribution of electrons EX: CO, oil

Hydrogen Bonds O - to H+ to 4 other water

Hydrogen Bonds Between slightly (+) H atom to a slightly (-) atom of a different molecule H-bonding of Water (nice animation)H-bonding of Water

Hydrogen Bonds Weak bonds But they are strong enough to cause water to needing a lot of heat to boil or to evaporate, and they form a less dense ice open lattice.

Cohesion Water is attracted to other water molecules (similar polar molecules) H-bonding between water molecules hold them together

Cohesion is why a waterfall, a stream, a water drop forms

Adhesion Attraction of unlike substances Like water to the sides of a glass tube Not so much with plastic Strong adhesion to glass

Water is a Good Solvent Can dissolve many substances

Water is the “Universal Solvent” Dissolving NaCl in water movieDissolving NaCl in water movie dissolve

Water is the Universal Solvent WHY? Can dissolve a lot of things What types of compounds are good at dissolving? –Polar –Ionic

How does detergent work? Soap has a water-loving (hydrophilic) and a water- hating end (hydrophobic). It attaches to the oil and then the water to wash away the oil.

Amphipathic Bipolar A molecule that is water-loving (polar) at one end and water- hating (non-polar, like oils) at the other end

Capillary Action The thinner the straw or tube the higher up capillary action will pull the water. Plant Capillarity

High Specific Heat Takes a lot of heat to raise the temperature of water (break the H-bonds) This is why coastal areas have mild climates

Surface Tension - the attraction of molecules to each other on a liquid's surface --creates a “film” Surface Tension

Floating Penny And paper clip H-bonds pull in water molecules and form a “film”

Water Strider Can stand on top of water Basilisk Lizard on WaterBasilisk Lizard on Water Water strider skimming across pondWater strider skimming across pond

Can exist as... Gas Liquid Solid Note in the solid ice, it is not much denser Due to H-bonds opening a lattice

High Heat of Vaporization Takes a high temperature to evaporate, or boil water Need to break those H-bonds

High Heat of Fusion Takes a low temperature to freeze water Those H-bonds must form

Water expands upon freezing If water worked like other liquids, then there would be no such thing as an ice berg, the ice cubes in your soft drink would sink to the bottom of the glass, and ponds would freeze from the bottom up!

Ice forms an Open lattice Below 4 o C Ice floats H-bonds are more stable in the solid form of water

Ice Expands

Water Molecules Can bond to four other water molecules H+ end attracts the O-ends + + -

Solutions A SOLUTE is the substance to be dissolved (sugar). The other is a SOLVENT. The solvent is the one doing the dissolving (water). As a rule of thumb there is usually more solvent than solute.

Solution = solvent + solute

SOLUTIONS When one substance dissolves another substance. SOLVENT + SOLUTE = SOLUTION Solvent=material in which the other material is being dissolved Solute=what is being dissolved

SALT SOLUTION Animation of Salt Dissolving in Water Dissolve Another Nice AnimationDissolve When water is the solvent, the solution is called an aqueous solution.

Salt Solution Which is the solvent? Which is the solute? Water is solvent. Salt is the solute.

FYI The solvent is defined as the substance that exists in a greater quantity than the solute(s) in the solution. Generally polar or ionic compounds will only dissolve in polar solvents.

Can you undissolve a dye? Undeniable Facts: Undeniable Friday: Un-dissolving Dye- a fact a dayUndeniable Facts: Undeniable Friday: Un-dissolving Dye- a fact a day Scroll down web page for explanation.

Dissociation (break into its ions) of Water Acids release H+ (hydronium) Bases release OH- (hydroxide)

Hydronium Ion = H+ Hydroxide Ion = OH- Animation of Dissociation of Water

pH * at pH 7.0, a solution is neutral * at lower pH (1-6), a solution is aacidic * at higher pH (8-14), a solution is basic

How much more? For every pH level lower there are 10 X’s more H+ ions So…… pH 2 has how many more H+ ions than pH 3? 10 So…pH 2 has how many more H+ ions than pH 4? 100

pH 1-6 = acid (the closer to “1” the stronger the acid) donates lots of H+ ions 8-14 = base (the closer to “14” the stronger the base) donate lots of OH- ions 7 = neutral or equal number of H+ and OH-

Buffer A substance that resists a change in pH when small quantities of acid or base are added (they are in the pH solutions for the duckweed)