Transcript Atoms and the Periodic Table PES 1

Atoms and the Periodic
Table
PES 1
Introduction to Atoms
Particle
Location
Charge
Symbol
Relative
Mass
(amu)
Proton
Nucleus
Positive (1+)
p+
1
Neutron
Nucleus
Neutral (0)
n
1
Electron
Electron
cloud
Negative(1-)
e-
1/1836
Atomic number

Atomic number
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Every atom of the
same element has the
same number of
protons in the nucleus
This identifies the
element
Example: carbon’s
atomic number is 6,
oxygen’s is 8 and
iron’s is 26
Mass Number & Isotopes

Mass number

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
The sum of the protons and
neutrons in the nucleus
Although the atomic
number does not change in
an element, the mass
number can change
Using the mass number
to find the number of
neutrons

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Take the mass number and
subtract the atomic number
So, 12 – 6 = 6 neutrons for
carbon
Isotopes

Isotopes: elements with the same number of protons, but
different number of neutrons
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Example: Carbon has 6 protons and 6 neutrons so it has a mass
number of 12 so we have Carbon-12, BUT an isotope of carbon
would have 6 protons and 7 neutrons so it has the mass number
of 13 and we have Carbon-13
Energy Levels
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Energy levels
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Located outside of the
nucleus – commonly called
“electron cloud”
1st energy level = 2
electrons
2nd energy level = 8
electrons
3rd energy level = 18
electrons
4th energy level = 32
electrons
Atomic Orbitals
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Orbital: the region of
space around the nucleus
where an electron is likely
to be found
Notice the maximum
number of electrons is
twice the number of
orbitals, that is because
each orbital can contain
two electrons at most
Energy
Level
Number
of
Orbitals
Max
Number
of
Electrons
1
1
2
2
4
8
3
9
18
4
16
32
Drawing Atomic Structures

Atomic structure:
Carbon
Practice
Organizing Elements

Mendeleev’s work
Organization of the
Periodic Table

Periods: the horizontal
rows

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Creates a pattern – the
atomic number increases
by one as you move from
each element
The pattern is repeated in
each period
Groups: (sometimes known
as families) the vertical
columns

Each group consists of
elements that have similar
properties
Organizing Elements

Reading an elements
square
Atomic Number
Chemical Symbol
26
Fe
Iron
Element Name
Atomic Mass
55.847
Metals
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Properties of Metals
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Physical properties:
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Shininess
Malleability: a material
that can be hammered
into a thin sheet
Ductility: a material that
can be drawn into a thin
wire
Conductivity: the ability
to transfer heat or
electricity
Metals
Metals

Properties of Metals

Chemical properties

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Reactivity: the ease or speed a metal has to combine or react
with other elements
Corrosion: rusting
Metals in the Periodic Table

Alkali metals: group 1, highly reactive
Metals

Metals in the Periodic Table

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Alkaline Earth Metals: group 2; highly reactive, but not as much
as group 1
Transition Metals: group 3-12; contain most familiar metals
Lanthanides: located in top row at the bottom of periodic table
Actinides: located in the bottom row at the bottom of the periodic
table (most are radioactive)
Nonmetals and Metalloids
Nonmetals and Metalloids
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Properties of nonmetals:
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Physical properties:
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Poor conductors of heat and electricity
Dull
Brittle: break easy
Chemical properties:
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Many nonmetals will for compounds with metals
Most common group of nonmetals is group 18 – the Noble
gases
Nonmetals and Metalloids
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The Noble Gases
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Do not make compounds under normal conditions
All noble gases exist in the Earth’s atmosphere, but in small
amounts
Properties of Metalloids
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Has properties of both metals and nonmetals
They are very similar to nonmetals, but have the ability to
conduct electricity and are called semiconductors
Radioactive Elements
Radioactive Elements
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
Radioactive decay: a natural process of unstable
isotopes releasing fast-moving particles and
energy
Types of radioactive decay

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Alpha decay
Beta decay
Gamma radiation
Radioactive Elements

Effects of nuclear radiation

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Alpha particles can cause burns, much like sunburns
Beta particles can pass through human skin and cause damage
to cells
Gamma rays are the most penetrating type of radiation, they can
cause intense damage to cells