Download Chapter 2: Elements are the building blocks of matter

Chapter 2: Elements are the
building blocks of matter
Chapter 2 – Elements are the building
blocks of matter
ELEMENTS
• A pure substance that cannot be broken down
or separated into simpler substances
• Made up of ONE kind of atom
• More than 115 elements known
Chemical Symbols
• Internationally recognized
• Consists of one or two letters
– First letter is always capitalized
– Second letter is always lowercase
• Some symbols are related to the English
names of the chemical (e.g. Helium is He), but
some are related to the latin names (e.g. Gold
is Au – for Aurum)
Elements can be:
metals, non-metals or metalloids
Metals, Non-metals & Metalloids
Metals are:
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Shiny
Malleable
Ductile
Usually solid
Good conductors of heat and electricity
Metals, Non-metals & Metalloids
Non-metals are:
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Gases or brittle solids
Dull
Non-malleable
Non-ductile
Poor conductors of heat and electricity
Metals, Non-metals & Metalloids
Metalloids are:
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Solids
Shiny or dull
Non-malleable and non-ductile
May conduct electricity
Poor conductors of heat
silicon
arsenic
Chapter 2.2 - The Periodic Table and
Chemical Properties
• Organizes the elements according to their
physical and chemical properties
• The one we use
was developed by
Dmitri Mendeleev
in 1867
Mendeleev’s Periodic Table
Mendeleev’s two main contributions:
• He organized all the known elements according
to properties and characteristics
• He recognized
the need to
leave spaces
for elements
not yet
discovered
The Periodic Table
• Includes each element’s
– Name
– Atomic number
- Symbol
- Atomic mass
Some things to remember:
• Atomic Number = # of protons
– # protons = # electrons (neutral charge!)
– Atomic numbers increase one by one
A carbon atom has 6
protons and 6 electrons!
Some things to remember:
• Atomic mass is the average mass of the atoms
of an element (measured in amu)
– When you round the atomic mass, you get the
mass number (which equals the number of
protons and neutrons in an atom of an element)
The atomic mass is
12.01 amu, so the mass
number rounds to 12...
So there are 12 protons
and neutrons in total
Some things to remember:
– So the # of neutrons can be calculated by:
mass number – # of protons (atomic #) = # neutrons
– The atomic mass /mass number tend to increase
with the atomic number , but there are exceptions
In a carbon atom, the
number of neutrons:
mass # - # protons = # neutrons
12 – 6 = 6 neutrons