ATOMIC STRUCTUREAND 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 10-23 GRAMS

SUBATOMIC PARTICLES

PARTICLE PROTON NEUTRON ELECRON

LOCATION NUCLEUS NUCLEUS THE ELECTRON SHELLS or “CLOUD”

MASS 1 AMU 1 AMU 1/1837 of an AMU

SYMBOL p+ n0 e-

CHARGE +1 0 – NEUTRAL -1

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