What is the chemical formula for water. Draw the structure of water What is the chemical formula for water? Draw the structure of water. Write down all the types of bonding that you know of.

What allows this drop of water to hang there without falling?

Surface Tension

Hydrogen Bonding in Water

Chemical Context of Life Matter (space & mass) Element; compound The atom Atomic number (# of protons); mass number (protons + neutrons) Isotopes (different # of neutrons); radioactive isotopes (nuclear decay) Energy (ability to do work); energy levels (electron states of potential energy)

Chemical Bonding Covalent Double covalent Nonpolar covalent Ionic Hydrogen van der Waals

Covalent Bonding Sharing pair of valence electrons Number of electrons required to complete an atom’s valence shell determines how many bonds will form Ex: Hydrogen & oxygen bonding in water; methane

Covalent bonding

Polar/nonpolar covalent bonds Electronegativity attraction for electrons Nonpolar covalent •electrons shared equally •Ex: diatomic H and O Polar covalent •one atom more electronegative than the other (charged) •Ex: water

Polar/nonpolar bonds

Ionic bonding High electronegativity difference strips valence electrons away from another atom Electron transfer creates ions (charged atoms) Cation (positive ion); anion (negative ion) Ex: Salts (sodium chloride)

Ionic bonds

Hydrogen bonds Hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom (oxygen or nitrogen)

van der Waals interactions Weak interactions between molecules or parts of molecules that are brought about by localized change fluctuations Due to the fact that electrons are constantly in motion and at any given instant, ever-changing “hot spots” of negative or positive charge may develop

Water Polar~ opposite ends, opposite charges Cohesion~ H+ bonds holding molecules together Adhesion~ H+ bonds holding molecules to another substance Surface tension~ measurement of the difficulty to break or stretch the surface of a liquid Specific heat~ amount of heat absorbed or lost to change temperature by 1oC Heat of vaporization~ quantity of heat required to convert 1g from liquid to gas states Density……….

Density Less dense as solid than liquid Due to hydrogen bonding Crystalline lattice keeps molecules at a distance

Acid/Base & pH Dissociation of water into a hydrogen ion and a hydroxide ion Acid: increases the hydrogen concentration of a solution Base: reduces the hydrogen ion concentration of a solution pH: “power of hydrogen” Buffers: substances that minimize H+ and OH- concentrations (accepts or donates H+ ions)

Two major parts of an atom Nucleus (not to scale) Electron Cloud

Three Major Sub-Atomic Particles Protons Neutrons Electrons

PROTON (p+) a single, relatively large particle with a positive charge that is found in the nucleus

THE PROTON p+ Fat (heavy) Positive  (charge) Doesn’t move (lazy)

NEUTRON (N°) a single, relatively large particle with a neutral charge that is found in the nucleus

THE NEUTRON N°  Fat (heavy) Neutral  (charge) Doesn’t move (lazy)

ELECTRON (e-) a single, very small particle with a negative charge that is found in a “cloud” around the nucleus

e- THE ELECTRON Skinny (very light) Negative  (charge) Moves a lot (runs around)

Review: Subatomic Particles N°  e-

Please complete the following table Protons Neutrons Electrons Where are they found? Mass Charge (attitude) Electron Cloud Nucleus Nucleus Heavy Heavy Very Light Positive  Neutral  Negative 

ATOMIC MASS # (A) The total mass of all of the subatomic particles in an atom (but really # of protons and neutrons)

ATOMIC NUMBER (Z) the number of protons in an atom (assuming the atom is neutral, # of p+ = # of e-)

Example: Sodium Na Atomic Mass # = p+ & N° 22.99 11 Atomic # = # of protons

Another Notation Atomic Mass # = p+ & N° Atomic # = # of protons

To calculate the number of neutrons, subtract the atomic number (smaller) from the atomic mass number (larger) A – Z = # of neutrons

Ex: How many neutrons does Sodium have? Mass # - Atomic # = #N° (You may need to round the atomic #) 22.99 23 - 11 = 12 N° Na 11

ION Atoms of the same element that differ in charge. (They have the same # of p+, but different # of e-)

Positive Ions (cations) Negative Ions (anions) Na+ (lost 1 e-) Ca2+ (lost 2 e-) Al3+ (lost 3 e-) Pb4+ (lost 4 e-) H+ (lost 1 e-) Cl- (gain 1 e-) O2- (gain 2 e-) P3- (gain 3 e-) S2- (gain 2 e-) OH- (gain 1 e-)

If an atom GAINS electrons, its overall charge becomes more negative If an atom GAINS electrons, its overall charge becomes more negative. If it LOSES electrons, its charge becomes more positive

ISOTOPE Atoms of the same element that differ in mass. (They have the same # of p+, but different # of N°)

Isotopes are CHEMICALLY the SAME as atoms, but DIFFER PHYSICALLY because they have different masses.

A few examples of isotopes…

Complete the following table Protons Neutrons Electrons Na+ Br w/ mass 84 O2- with mass 13