Chapter 4

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Chapter 4
Elements and the Periodic Table
8th Grade Science
Introduction to Atoms
• Greek philosopher named __________
Democritus
proposed that matter is made up of tiny
particles that cannot be made any smaller
• ________
“Atomos” - means “uncuttable”
Atom - smallest particle of an element
• _____
Atomic Theory - formed in the 1600’s as a
• ___________
series of models developed from experimental
evidence.
Atomic Theory
• As more experiments were conducted and
evidence collected, the theory and models
were revised.
Dalton’s Atomic Theory - John Dalton, English
• ________________
chemist, inferred that atoms had certain
characteristics.
• Dalton’s atomic theory is still accepted today!
• Atoms were like smooth, hard balls that
cannot be broken down
Summary of Dalton’s Ideas page 103
• All elements are composed of atoms that cannot
be ______.
divided
• All atoms of the same element are exactly alike
and have the same ____.
mass
changed
• An atom of one element cannot be _________
into an atom of a different element – only
rearranged.
• Every ________
compound is composed of atoms of
elements
different _________
combined in a specific
________.
ratio
Thomson Model
JJ Thomson
• ___________
- 1897 atoms have negatively
charged electrons embedded in a positive
sphere.
• _______
electrons - negatively charged particles
Rutherford and the Nucleus
• 1911 - ____________
Ernest Rutherford - a student of Thomson,
found evidence that contradicted Thomson’s
model.
• ______________
Gold Foil Experiment - beam of positively charged
particles aimed at a thin sheet of gold foil.
Most of the particles passed through the foil
as expected. However, a few particles were
deflected
_______.
Conclusions from the Foil Experiment
• Since like charges _____
repel each other,
Rutherford concluded that an atom’s
positive
_________
charges must be clustered in the
_____
center of the atom.
• ______
nucleus - center of the atom
• ________
electrons - no mass
protons
• ________
- positively charged particles that
have mass and are located in the nucleus of
the atom.
Rutherford’s Model
Bohr’s Model
Neils Bohr
• ___________
- 1913, Danish Scientist, student
of both Thomson and Rutherford – electrons
orbit
move around the nucleus in certain _____
based on energy levels.
• Bohr’s Model resembles planets orbiting the
sun or layers of an onion.
Cloud of Electrons
• 1920’s – atomic model changed again
• Scientists determined that electrons DO NOT
orbit the nucleus like planets.
• _________
can be anywhere in a cloudlike region
Electrons
around the __________.
nucleus
electrons movement is related to its
• An _______
_________
Energy level - specific amount of energy that it
has.
Energy level
• ____________
affects the atoms reactions with
other atoms.
The Modern Atomic Model
James Chadwick discovered another particle in
• ___________
the nucleus of atoms.
• _________
- particle discovered by Chadwick
Neutrons
that has no electrical charge and nearly the
Protons
same mass as _______.
• _______________
Modern Atomic Model - consists of a nucleus that
contains protons and neutrons surrounded by
a cloudlike region of moving electrons.
Particle Charges
• In an tom the number of ________
equals the
protons
Electrons
number of __________.
• _________
have a positive charge and a mass
____
Protons
• _________
have a negative charge and very
electrons
mass
little _______.
• _________
have neutral charge and a mass
Neutrons
that equals that of protons.
Positive
Protons
• ________
charge of ________
equals the
________
charge of _________.
negative
Electrons
Masses and Charges
Particle
Symbol
Charge
Relative
Mass
(amu)
Proton
p⁺
1₊
1
Neutron
n
0
1
Electron
e⁻
1₋
1/1,836
• Charges balance making
the atom neutral
• Number of neutrons does
not have to equal the
number of protons
• Neutrons do not affect
the charge of an atom
because they have no
charge
• Approximately 2,000 e⁻
equal mass of one proton.
Atomic Number
• Every atom of an element has the same
number of _________.
protons
Atomic Number
• _____________
- number of protons in the
nucleus of an atom.
• Atomic number identifies an _________.
element
• _______
Isotopes - atoms with the same number of
protons but a different number of neutrons.
Mass number
• __________-sum
of the protons and neutrons
in the nucleus of an atom.
Patterns in the Elements
_____________
Dmitri Mendelev - Russian scientist discovered a set
of patterns that applied to all elements.
Mendelev arranged the elements in order of
increasing __________.
Atomic mass
Periodic table
____________
- organization of the elements
where the properties of the elements repeat in
each row of the table.
___________
Henry Moseley - Brittish scientist discovered a way to
measure the positive charge on an atom’s
nucleus – the atomic number.
Periodic Table of Elements
• After Moseley’s discovery, the periodic table
was rearranged from Atomic
________
_________.
mass toAtomic
number
• Properties of an element can be predicted
based on its place in the ___________.
Periodic table
• Periodic table is arranged according to
___________
Atomic number increasing from left to right.
periods
• ________
- horizontal rows on the periodic
table where the properties of the elements
change in a set pattern.
Organization of the Periodic Table
• Elements on the left side of the periodic table are
_______________.
Highly reactive metals
• Elements in the middle of the periodic table are
______________.
Less reactive metals
• Elements on the right side of the periodic table
are _________________.
Metalloids and non-metals
• ______
Groups - 18 vertical columns or “families” on the
periodic table with similar characteristics such as
rate of reaction. (except lanthanides and
actinides).
Reading the Periodic Table
• Each element in the periodic table has all of
the following:
– ____________
Atomic Number - number of protons in the nucleus
Chemical Symbol - 1 or 2 letter representation
– _____________
– ____________
Element Name
– __________
Atomic Mass - average mass of all of the isotopes
of the element.
Metals
• Physical properties of metals:
– ________
shininess
– __________
malleability - material can be hammered or rolled
into flat sheets and other shapes.
ductility - material can be pulled out or drawn
– _______
into a thin wire
– __________
conductivity - ability of an object to transfer heat
or electricity to another object.
– ___________
Mercury (Hg) - metal that is liquid at room
temperature
Chemical Properties of Metals
• _________
- the ease or speed of an element
reactivity
to combine or react to other elements and
compounds.
elements
• Metals usually react by losing ________
to
other atoms.
• Sodium (Na) is very reactive where gold (Au)
and platinum (Pt) are much less reactive.
• __________
- the destruction of a metal
corrosion
because of its reactivity.
Metals in the Periodic Table
• _______
reactivity of metals decreases from left to right
on the periodic table.
• ____________
- metals in Group 1 on the
Alkali Metals
periodic table that react with other elements
by losing one ______.
electron
• Alkali metals are never found in __________
uncombined
elements in nature – only in compounds.
• ___________________
Sodium(Na) and potassium (K) - two most important
alkali metals – important for life processes.
Alkali Earth Metals
Alkali Earth Metals - Group 2 on the periodic
• ______________
table that react with other metals by losing
two electrons.
• Not as reactive as metals in __________
but
Group 1
more reactive than ,most other metals.
• Never found uncombined in nature.
• ______________________
Magnesium (Mg) and Calcium (Ca) - two most
common alkali earth metals.
Other Elements on the periodic table
• ____________
Transition Metals - elements in Group 3 through
12. These metals are hard and shiny, good
conductors of electricity, less reactive than
metals in Groups 1 and 2. ________
is an
Iron (Fe)
example of a very important transition metal.
• _______________
Groups 13, 14, and 15 - only some are metals
such as aluminum, tin and lead
• _________
Lanthanides - two rows of elements at the
bottom of the periodic table.
Lanthanides
• __________
- soft, malleable shiny metals
Lanthanides
with high conductivity.
• Lanthanides mix with other metals to form
_____.
alloys
• _____
alloy - mixture of a metal and at least one
other element, usually another metal.
Actinides
• _________
- only four occur naturally on earth
– all others were created artificially. These
elements are VERY unstable. Ex. Uranium
Synthetic Elements
Synthesized
• ____________
- elements that follow uranium
that are not found naturally on Earth – when
nuclear particles are forced to crash into one
another.
• _____________
Particle accelerator - powerful machines used by
scientists to move atomic nuclei to very high
speeds.
Non-metals and Metalloids
• Physical properties of non-metals:
Poor conductors
– ______________
– _____________________
Reactive with other elements
– ______________
Dull and brittle
– Many non-metals are common elements on Earth
10 of 16
gases at room
– ________non-metals
are ______
temperature.
Bromine (Br) - only non-metal that is liquid at
– ___________
room temperature
Chemical Properties of Non-Metals
gain
share
• Atoms of non-metals usually _____
or ______
electrons with atoms that they react with.
• When metals and non-metals react,
_________
move from the metal atoms to the
electrons
non-metal atoms.
• Non-metals can also form compounds with
other non-metals.
Families of Non-metals
• 1. _______________
- Group 14 only carbon
The Carbon Family
is a non-metal. atoms that gain, lose, or share
four
____electrons
when reacting with other
elements.
• 2. ______________
The Nitrogen Family - Group 15 contains two
non-metals, nitrogen and phosphorous. These
atoms usually gain, lose or share _______
three
electrons when reacting with other elements.
• 80% of the atmosphere is nitrogen gas (N₂)
Families of Non-Metals continued
The Oxygen Family - Group 16 contains three
• 3. _____________
non-metals – oxygen, sulfur and selenium.
Elements in the oxygen family usually gain or
share ___
two electrons.
• _________
is highly reactive – it can combine
oxygen
with nearly any other element.
most most abundant element in
• Oxygen is the ____
the atmosphere (Nitrogen is first)
The Halogen Family
• 4. ______________
The Halogen Family - Group 17 contains flourine,
chlorine, bromine, iodine, and astatine (not a
non-metal). Halogen
_______ means “salt forming”.
Halogen atoms usually gain or share ____
one
electron when it reacts with other elements.
• All halogens are __________
Very reactive and can be
dangerous to humans.
• Many compounds that contain halogens can be
useful to humans – salt, flourine in water, calcium
chloride.
Noble Gases
• __________
Noble Gases - elements in Group 18 that do not
ordinarily form compounds because atoms of
noble gases do not usually gain, lose, or share
electrons.
unreactive
• These gases are usually ___________.
• All of the noble gases exist in the Earth’s
atmosphere
___________.
• Noble gases were not discovered until late 1800’s
because they are _______
unreactive and ________.
scarce
Hydrogen
Hydrogen (H) - in the upper left corner of the
• __________
periodic table.
• Hydrogen makes up more than 90%
___ of the
atoms in the universe.
Pure element
• Hydrogen is rarely found as a ___________.
Metalloids
• ____________
- along the border between
Metalloids
metals and non-metals.
7
• There are ___
metalloids and they have
characteristics of both metals and non-metals.
• All metalloids are solid
____ at room temperature.
• Metalloids are also brittle, hard, somewhat
reactive, varying ability to conduct heat and
electricity
Silicon (Si) - most common metalloid
• ________
Semiconductors
Semi-conductors - substances that conduct
• ____________
electricity under some conditions but not
under others.
• ________
metalloids are used as semiconductors
because of their physical properties.
• Semiconductors are used to make _________,
lasers
Computer chips
transmitters
_____________,
and ___________.
Radioactive Elements
• _____________
Radioactive Decay - the atomic nuclei of unstable
isotopes release fast moving particles and energy.
Henri Becquerel
• _____________
- French scientist in 1896
discovered the effects of radioactive decay while
he was studying a mineral that contained
uranium.
Marie Curie is the
• ___________
- named after __________
radioactivity
spontaneous emission of radiation by an unstable
nucleus such as uranium.
Types of Radioactive Decay
• Natural radioactive decay can produce
___________,
____________,
and
Alpha particles
Beta particles
Gamma rays
___________.
• _________
Alpha decay - an alpha particle consists of two
protons and two neutrons and is positively
charged. The release of an alpha particle by an
atom is decreases the atomic number by __
2
4
and the atomic mass by __
Beta Decay
• __________
- a neutron inside of the nucleus
Beta Decay
of an unstable atom changes into a negatively
charged beta particle and a proton.
• __________
Beta particle - fast moving electron given off
by a nucleus during radioactive decay.
• Nucleus has one _____
neutron and one ____
less
more
proton – therefore, the atomic mass stays the
same but the atomic number increases by __
1
Gamma Radiation
Gamma Radiation - consists of high-energy
• _____________
waves – has no charge and does not cause a
change in either atomic mass or atomic
number.
Effects of Nuclear Radiation
Radioactive Isotopes
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