ATOMIC STRUCTURE AND ELECTRON CONFIGURATION

ATOMIC BASICS EARLY IDEAS FROM GREEK PHILOSOPHERS WERE THAT AIR, FIRE, WATER AND EARTH WERE THE FOUR “ELEMENTS” MODERN SCIENCE HAS GIVE US THE PERIODIC TABLE AS A REPRESENTATION OF THE ELEMENTS THAT COMPOSE ALL THINGS CURRENTLY THERE ARE 117 ELEMENTS (NO #117), ALL ARE HOMOATOMIC OVERVIEW OF THE BASIC STRUCTURE: THE ATOM IS INCREDIBLY SMALL THE NUCLEUS IS MUCH SMALLER AND VERY DENSE ELECTRONS ARE INCREDIBLY SMALL AND ALWAYS IN MOTION AMU –ATOMIC MASS UNIT- SYSTEM USED TO MEASURE MASS OF PARTICLES. IT IS EQUAL TO 1.67 x GRAMS

SUBATOMIC PARTICLES PARTICLEPROTONNEUTRONELECRON LOCATIONNUCLEUS THE ELECTRON SHELLS or “CLOUD” MASS1 AMU 1/1837 of an AMU SYMBOLp+p+ n0n0 e-e- CHARGE+10 – NEUTRAL ROLE IT PLAYS -More than one -Defines the element -It is the atomic number -Gives positive charge to nucleus -Provides mass to the atom -Main role is to add mass -Differing numbers create isotopes -Can cause radioactivity in some elements (H1, H2, H3) -Used in bonding -Gives chemical properties -Has a negative charge to counter protons -Can be lost or gained to create ions

MODERN ATOMIC STRUCTURE AND THEORY  ACCORDING TO MODERN ATOMIC THEORY, WE CAN DIVIDE THE ATOM INTO TWO DISTINCT AREAS:  THE NUCLEUS  VERY SMALL AND VERY DENSE, THE CENTER OF THE ATOM  CONTAINS ONLY 2 PARTICLES:  PROTONS – ELEMENTS CONTAIN A DISTINCT NUMBER (ATOMIC NUMBER)  NEUTRONS – NUMBER CAN BE VARIABLE, CREATING ISOTOPES  ELECTRON SHELLS or “CLOUD”  CONTAIN ONLY ELECTRONS  ESSENTIALLY HAVE NO MASS  PARTICLES ARE ALWAYS IN MOTION  WE CAN’T FIND THE ACTUAL ELECTRON, WE LOOK FOR THEM IN AREAS

STILL LIFE ATOMIC MODEL

PROBLEMS WITH MODELS  NOT TO TRUE SIZE  CANNOT ACCURATELY MIMIC ELECTRON MOTION  2 DIMENSIONAL  DO NOT SHOW NUCLUES MOTION/VIBRATION

FILLING THE ELECTRON SHELLS (RULES)  AUFBAU PRINCIPLE : ELECTRONS ENTER ORBITALS OF THE LOWEST ENERGY LEVEL FIRST  PAULI EXCLUSION : EACH ORBITAL MAY ONLY HOLD A MAXIMUM OF 2 ELECTRONS WITH OPPOSITE SPINS  HUNDS RULE : EACH ORBITAL FILLS WITH 1 ELECTRON BEFORE FILLING AN ORBITAL WITH A SECOND ELECTRON