Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
The Atom • ICAN describe the structure of the atom and identify the atomic number and atomic mass number. The Atom • All matter is composed of ATOMS. • An atom is the SMALLEST PARTICLE of matter that has ALL OF MATTER’S PROPERTIES. • The idea of the atom has changed a great deal over time. • The idea of the atom was first proposed more than 2000 YEARS AGO by the Greek Philosopher DEMOCRITUS. • Up until the time of Democritus, philosophers believed all matter was made up of four basic elements: • EARTH • AIR • WATER • FIRE • Democritus proposed all matter was composed of TINY, INDIVISIBLE SPHERES he called ATOMS. • Unfortunately, Democritus couldn’t TEST his idea and it soon faded into the past. • It was until the EARLY 1800s that the idea of the atom resurfaced. • An ENGLISH TEACHER-SCIENTIST named JOHN DALTON revived the ancient idea of the atom and proposed what came to known as DALTON’S ATOMIC THEORY. • Over the years since Dalton’s time the idea of the atoms has been TESTED and REVISED many times as new information was obtained. THE MODERN IDEA OF THE ATOM • The ATOM is composed of even smaller particles known as SUB-ATOMIC PARTICLES. • While more than 100 subatomic particles have been identified, we will focus on ONLY THREE: • PROTONS • NEUTRONS • ELECTRONS PARTS OF THE ATOM • The atom is divided into TWO PARTS: • 1. The NUCLEUS – the SMALL, DENSE and SOLID central core of the atom. • 2. The ELECTRON CLOUD – a LARGE AREA OF SPACE surrounding the nucleus of the atom. Electron Cloud – about 10,000 times bigger than the nucleus! Nucleus The NUCLEUS • The NUCLEUS is made up of PROTONS and NEUTRONS. • PROTONS – POSITIVELY charged particles. Their symbol is P+. • The NUMBER OF PROTONS an atom has is known as it’s ATOMIC NUMBER. • The AN tells which of the 109 ELEMENTS an atom belongs to. • NEUTRONS – NEUTRAL (no charge) particles also found in the nucleus. Their symbol is No. *The total number of Protons plus the total number of Neutrons give us the atom’s ATOMIC MASS NUMBER (mass number). • The AMN accounts for over 99% of the mass of an atom. The ELECTRON CLOUD • Surrounding the nucleus is an area of mostly EMPTY SPACE. • Within this space, ELECTRONS move around the nucleus of the atom much like a swarm of bees around a hive. • This area is known as the ELECTRON CLOUD. • Electrons are very small NEGATIVELY charged particles. • It takes 1837 electrons to weigh as much as 1 proton or neutron! • The symbol for an electron is e-. • In most atoms, the number of P+ and e- is EQUAL…therefore the atom has NO OVERALL CHARGE (the “+” charges balance out the “-” charges). How Elements Are Arranged On The Periodic Table • On the Periodic Table of the Elements, the elements are arranged by INCREASING ATOMIC NUMBER beginning at element number 1 – HYDROGEN up to element 109 – MEITNERIUM. – The AN usually appears at the TOP of each box on the periodic table. – The AMN usually appears at the BOTTOM of each box on the periodic table.