Part-I-Introduction-to-Organic-Chemistry.pdf

Prepare by: Almera Pryle P. Saluta, RMT, MPA WHAT IS AN ATOM? - Fundamental building blocks of chemistry - Matter itself is made of a collection of different type of atoms - 118 kinds Elements found in the Periodic Table - Cannot be seen with the...

Prepare by: Almera Pryle P. Saluta, RMT, MPA WHAT IS AN ATOM? - Fundamental building blocks of chemistry - Matter itself is made of a collection of different type of atoms - 118 kinds Elements found in the Periodic Table - Cannot be seen with the naked eye PARTS OF AN ATOM  PARTS OF AN ATOM - Consists of a positively charged nucleus, surrounded by one or more negatively charged particles called electrons. - Nucleus of an atom contains protons and neutrons making up most of an atom’s mass  PARTS OF AN ATOM - Protons and neutrons have nearly equal masses, but they differ in charge - Neutron has no charge - Proton has a positive charge - Electron has negative charge PARTS OF AN ATOM  ATOMIC SIZE - All atoms are roughly the same size - Unit of length for measuring atomic sizes: Angstrom (Å) 1 × 10-10 meters - The diameter of an atom is approximately 2-3 Å  ATOMIC SIZE - Atomic radius: 1 to 2.5 Angstroms (Å) - Nucleus radius: 10 Å -5 CHARGE AND MASS OF THREE SUB ATOMIC PARTICLES: § Actual masses of atoms and subatomic particles are very small, often describe their masses by comparison rather than in SI units, hence the term relative mass. § Atomic mass unit (amu) is the term used when talking about relative masses § If a proton is assigned a mass of 1.007, then a neutron will have a relative mass of 1.008 and an electron a mass of 5.45 X 10-4.  CHARGE AND MASS OF THREE SUB ATOMIC PARTICLES: § Using this unit, a proton has a mass of 1.007 amu, a neutron a mass of 1.008 amu, and an electron a mass of 5.45 X 10-4 amu. § Charges are given relative to one another. § If a proton has a charge of +1, then an electron has a charge of -1. CHARGE AND MASS OF THREE SUB ATOMIC PARTICLES: Relative Actual Particle Charge Mass Mass (g) (amu) Electrons 9.108x10 -28 -1 0.000549 Protons 1.6726x10 -24 +1 1.00782 Neutrons 1.6726x10 -24 0 1.00867  MASS & MATTER § Mass – a basic physical property of matter § Matter – anything that occupies space, has mass and can be in three states: Solid, Liquid, or Gas  ATOMIC NUMBER (Z) §Represented by Z §Identifies the element §Equal to the number of protons §Usually a whole number ATOMIC NUMBER (Z) ATOMIC NUMBER (Z)  ATOMIC MASS (A) §The mass of an atom or a molecule §Used to find the average mass of elements and molecules and to solve stoichiometry problems AVERAGE ATOMIC MASS (A) AKA ATOMIC WEIGHT §Measured in atomic mass units (amu), also called daltons (usually whole number) §The average that reflects the typical ratio of natural abundances of an element’s isotope AVERAGE ATOMIC MASS (A) AKA ATOMIC WEIGHT §1961 - the standard unit of atomic mass has been one-twelfth the mass of an atom of the isotope carbon-12 §Fundamental to chemistry, because most chemical reactions take place in accordance with simple numerical relationships among atoms AVERAGE ATOMIC MASS (A) AKA ATOMIC WEIGHT §Isotope - one of two or more species of atoms of the same chemical element that have different atomic mass numbers (protons + neutrons). AVERAGE ATOMIC MASS (A) AKA ATOMIC WEIGHT Democritus § first to clearly propose the idea of an atom, coining the word, ‘Atomos’ (which means uncuttable) J. J. Thomson (1987) § Discoveredthe existence of the electron, marking the beginning of modern atomic physics §Negatively charged electrons follow a random pattern within defined energy shells around the nucleus J. J. Thomson (1987) §Most properties of atoms are based on the number and arrangement of their electrons. §Electron Mass = 9.1 × 10-28 kg Sir Ernest Rutherford (1919) - Proved the existence of a positively charged particle, a PROTON, in the nucleus - The proton's charge is equal but opposite to the negative charge of the electron Sir Ernest Rutherford (1919) - The number of protons in the nucleus of an atom determines what kind of chemical element it is. - Proton Mass = 1.67 × 10-24 kg Sir James Chadwick - 1932 - British Physicist that proved that neutron, another type of particle found in the nucleus, that it carries no electrical charge and has the same mass as the proton Sir James Chadwick - Neutron is not repelled by the cloud of electrons or by the nucleus, making it a useful tool for probing the structure of the atom - Neutron Mass/Proton Mass = 1.67 × 10-24 kg QUARKS - Internal structure of individual protons and neutrons - have six types - cannot be freed and studied in isolation - current research continues into the structure of the atom