Transcript Topic 2.0 - SchoolRack

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What is an observation?
Observation – gathering information using
senses
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What is a theory?
Theory – explanation of
observations that has been
supported by repeated
experimental results
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Models – a diagram, picture or 3-D structure
to represent ideas
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Scientists use models to explain ideas hard to
explain or imagine like the atom.
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8000BC – Stone Age – fire
was used to shape tools
4500 BC – Bronze Age –
copper was heated with tin
to create a new metal
(strong)
1200BC – Iron Age – steel
was produced by
combining iron and carbon
(stronger/sharper)
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500BC – Democritus – used
word “atomos” to describe
smallest unit of matter
 -Atoms could be put together to
make new matter with different
properties
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350BC – Aristotle – believed matter was made
from earth, air, fire and water.
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1600s – Alchemy – was a mixture of magic
and science
 -created Plaster of Paris
 -Believed metals  gold
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1660s – Robert Boyle
 -Studied gases and
pressure
 -Believed matter was
made of particles
 -These particles could
combine to make new
matter
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Antoine Laurent
Lavoisier
 Developed a system
for naming chemicals
▪ “Father of Modern
Chemistry”
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John Dalton
 >Matter was made of elements
 >Elements are pure substances of
one atom
 >Every atom in an element are
identical
 > Billiard Ball model
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J.J. Thomson
 Created the “Raisin Bun Model”
 Discovered first subatomic
particle - the electron
 Believed atoms were positive
spheres with negative electrons
embedded.
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Hantaro Nagaoka – believed the center of the
atom was positive and electrons (negative)
orbited the center
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Ernest Rutherford
 -Atoms – mainly empty space with a tiny positive
center (nucleus); electrons are randomly around it
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Neils Bohr
-believed electrons orbit around nucleus in energy
levels
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James Chadwick
 -discovered the nucleus contained protons (+) and
neutrons (no charge)
*The Atom *
 Is the smallest unit of matter and is made of 3
subatomic particles:
▪ Electrons (-) orbit around the outside of the nucleus
▪ Protons (+) part of the nucleus
▪ Neutrons (o) part of the nucleus
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Each element is made of an atom with a
specific number of protons, neutrons and
electrons
Is neutral – has same # of electrons as protons
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WHY do we learn about the history of
chemistry?
What is the purpose of re-learning history?
What does history tell us about the nature of
science?
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Is the arrangement of elements according to
patterns in behavior
Was developed by Dmitri Mendeleev in
1880’s
His idea was based on patterns in melting
points, density and color
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Arranged in the following patterns:
1) Metals/Non-metals
-metals are left of staircase =
* malleable, ductile and conductive
-non-metals are right of staircase =
* brittle and non-conductive
-metalloids – are on staircase; have properties of both
metals and non-metals
2) Periods – horizontal rows
># of protons increases as you go left to right
>Left side are metals; right side are non-metals
>The reactivity of metals decreases as you go right
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3) Groups / Families – vertical columns; similar
properties within a group
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Alkali Metals – most reactive metals; react with air and
water
Alkali Earth Metals – less reactive metals
Halogens – most reactive non-metals;
Noble gases- Most stable and unreactive elements
ALKALI EARTH
ALKALI
NOBLE GASES
HALOGENS
Increase in size, reactivity
Increase in size, # of atomic particles 
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Atomic number – the number of protons
 Since atoms are neutral, is also # of electrons
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Atomic mass – the number of protons +
neutrons
To find # of neutrons:
Atomic mass – atomic # = neutrons
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Ex. What is the symbol for aluminum? Iron?
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What elements are in each of the following
groups:
 A) Alkali earth
 B) Alkali
 C) Halogens
 D) Noble gases
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What is the atomic number of sodium?
 Atomic mass?
Number of protons, neutrons and electrons?
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Is sulphur a metal or non-metal?
How many protons, neutrons and electrons
does nitrogen have?