Transcript The Atom - Magoffin County Schools

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.