SBI 4U1 – Unit 1

Lesson 1

Basic Concepts in Chemistry

Atomic Theory

• All living things are made of matter• All matter is made of atoms• Therefore all living things consist of atoms• Therefore all living things are governed

by the same laws of the physical universe that govern the interactions of atoms and molecules

The Laws of Thermodynamics

Basic Chemistry Review

• 1.1 Chemical Fundaments• Bohr Diagrams allow us to determine the valence

or chemically active electrons of an element– Valence number refers to the number of bonds an

element is capable of forming

• X = element symbol• A = # of protons

= # of positive charge

= # of electrons in neutral atoms• Z = atomic mass

XA

Z

Basic Chemistry Review - Ions

• Elements or compounds that have acquired an electric charge

• Due to the gain or loss of electrons– E.g. NaCl will dissociate in solution to form to

monatomic ions:– Na+ ions have lost one electron to the chlorine ions– Cl- ions have gained one electron from sodium ions

Basic Chemistry Review - Ions

• Many biologically active ions are polyatomic– Phosphate PO4

3-

– Sulfate SO42-

– Nitrate NO3-

– Hydroxyl OH-

Basic Chemistry Review - Isotopes• Atoms of elements with an atomic mass that is

different from the most commonly found form• E.g. 3 isotopes of carbon

– C – 12; 6 protons, 6 neutrons– C – 13; 6 protons, 7 neutrons– C – 14; 6 protons, 8 neutrons

• Isotopes have a variety of uses– Diagnosis – radioactive isotopes can be used to “light

up” organs and tissues of interest– Treatment – used to treat a variety of soft tissue

disorders including cancers– Research – radioactive isotopes can be used to track

changes to biological molecules in metabolic pathways

Basic Chemistry Review - Bonding

• Bonding allows atoms to form stable configurations as larger compounds

• A sharing or distribution of valence electrons in order to stabilize outer electron orbitals

• Two main types of bonds– Intramolecular – within the molecule

• Ionic• Covalent• Polar Covalent

– Intermolecular – between molecules• Di-pole Hydrogen bonds• Vander Waals

Basic Chemistry Review - Bonding

Electronegativity• A measure of the tendency of a particle to attract

a bonding pair of electrons• Scale ranges from 0 to 4.0• Cesium has the lowest value 0.7• Flourine the highest at 3.98• ΔE values determine the type of bond• Pauling Scale is generally used to determine

electronegativity values as experienced by atoms in molecules

Basic Chemistry Review - Bonding

Ionic Bonds– ΔE>1.7 – disassociate in water– Useful for biological reactions but not for creating

biological structures

Covalent Bonds– ΔE = 0 – very strong and stable – Can be single, double or triple– Most common form of bonding in biological

molecules

Polar Covalent– 0>ΔE<1.7 – Similar to covalent but the distribution of electrons is

not equal resulting in a localized electric charge