1. The Atom

2. ICAN describe the structure of the atom and identify the atomic number and atomic mass number.

3. 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.

4. Up until the time of Democritus, philosophers believed all matter was made up of four basic elements: EARTH AIR WATER FIRE

5. 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.

6. Over the years since Dalton’s time the idea of the atoms has been TESTED and REVISED many times as new information was obtained.

7. 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

8. 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.

9. Electron Cloud – about 10,000 times bigger than the nucleus! Nucleus

10. 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.

11. NEUTRONS – NEUTRAL (no charge) particles also found in the nucleus. Their symbol is N o. * 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.

12. 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.

13. 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).

14. 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.