Transcript Understanding the Atom

Understanding the Atom
4-1: Basic Units of Matter
4-1 Vocabulary
Matter
atom
nucleus
proton
neutron
electron
Democritus
Dalton
Lavoisier
Law of Conservation of Mass
What is the current atomic
model?
Matter is anything that has mass and takes
up space (such as solids, liquids and gases)
Sound, heat and light are not matter - they are
forms of energy.
An atom is a small particle that makes up
all matter.
Atoms are mostly empty space surrounding
a massive central region of the atom called
the nucleus.
What is the current atomic
model? (cont’d)
Atoms contain three kinds of particles, two
in the nucleus, and one outside the center
of the atom.
Positively charged particles in the nucleus
are protons.
Neutral particle in the nucleus is the
neutron.
Negatively charged particles that move in
the space outside an atom’s nucleus is the
electrons.
What is the current atomic
model? (cont’d)
An electron has about 1/2,000 the
mass of a neutron or proton.
Interactive Atom
Is there historical evidence of
atoms?
The Greek philosopher Democritus first
(460 – 370 B.C.) coined the word atom,
based on the Greek word atoma, meaning
“indivisible” or “uncuttable”.
Democritus proposed that atoms were small,
solid spheres.
The atom as Democritus described it was
indivisible, meaning it was the smallest
possible piece of matter that could not be
cut into smaller pieces.
Is there historical evidence of
atoms? (cont’d)
The French scientist Antoine
Lavoisier conducted experiments that
led to the Law of Conservation of
Mass. It says that in any chemical
reaction, the mass of the products of
the reaction will always be equal to
the mass of the materials at the
beginning of the reaction.
Is there historical evidence of
atoms? (cont’d)
The law of definite proportions, uncovered
by French chemist J.L. Proust, states that
pure compounds always contain the same
elements in the same proportions by mass.
Water’s formula is H2O which means there are
two Hydrogen atoms and one Oxygen atom in
every molecule of water.
Water from your kitchen sink is the same as
water from a glacier on Mars.
Is there historical evidence of
atoms? (cont’d)
English schoolteacher and scientist
John Dalton did many experiments on
gases that led to a new and more
complete model of the atom.
Dalton’s model had 5 major points.
Dalton’s Atomic Model
All matter is made up of atoms.
Atoms are neither created or destroyed in
chemical reactions. (Law of Conservation of Mass)
Atoms of different elements combine in
whole-number ratios. (Law of definite proportions)
Each element is made of a different type
of atom.
The atoms of different elements have
different masses and properties.
Dalton’s Atomic Model
(cont’d)
Dalton used symbols to represent
different elements, making it easier to
write and communicate about the elements.
4-1: Lesson Review Questions
Which is NOT a particle in an atom?
A positron
B neutron
C electron
D proton
4-1: Lesson Review Questions
Which law states that the total mass of the
starting materials equals the total mass of the
product in a chemical reaction?
A Dalton’s atomic model
B the law of conservation
of mass
C the law of definite
proportions
D Democritus’ law
4-1: Lesson Review Questions
____ make up the nucleus of
an atom.
A Protons and electrons
B Neutrons and electrons
C Protons and neutrons
D Neutrons and photons
Homework
Answer the three multiple choice lesson
review questions.
Write a “Step-Up-To-Writing” style
paragraph answering the following question
regarding your notes: “Why are symbols
for concepts and objects, such as
elements, atoms, and their electrons,
important tools to help people
communicate? ”