Transcript CHAPTER 5 – THE PERIODIC TABLE

CHAPTER 5 – THE PERIODIC TABLE
• Read introduction
page 158
• Early 1800’s
German chemist
J.W. Dobereiner
discovered a triad
relationship
between elements
• 1864 – Newlands
discovered the Law of
Octaves – repeating
pattern of chemical
reactivity (every 8
elements)
• 2 bonus points, find
the mistake in the
description of Law of
Octaves on the top of
page 161
• 1869 – Russian
chemist/teacher Dmitri
Mendeleev created
the first periodic table
• He arranged the table
in order of increasing
mass and chemical
properties
• He left blank spaces
and predicted the
existence of
undiscovered
elements
• Moseley discovered
atomic number by
studying the frequency
of x-rays produced
when metals were
bombarded with high
energy electrons.
• He hypothesized that
this was due to a
different positive
charge in each
nucleus.
• The Periodic Law – When
elements are arranged in order
of increasing atomic #, their
physical and chemical properties
show a periodic pattern.
• Do not memorize lots of facts
about elements – instead learn
to predict an element’s
properties by its position on the
periodic chart.
Vertical columns – families have the same outer
electron configuration
– Have similar physical properties and chemistry
H
Li
Na
1S1
[He] 2S1
[Ne] 3S1
K
[Ar] 4S1
Identify the s, p, d, and f block
Rb
Cs
[Kr] 5S1 [Xe] 6S1
Horizontal rows are called periods – row number is the
energy level for the s and p block elements.
d energy level is n – 1
f energy level is n – 2
Can read electron configuration directly from the chart
Group 1A – alkali metals
lose one electron
2A – alkaline earth metals
lose two electrons
7A – halogens
gain one electron
8A – noble gases
do not react
• Chemical reaction – competition for
electrons
• Electronegativity – a measure of an
atom’s ability to compete for electrons
• F has highest electronegativity
• Cs and Fr have lowest
• As we approach F on the chart,
electronegativity increases
Three groups of Elements
Metals
•lose electrons
•Shinny (luster)
•Malleable
•Conduct electricity
Non-metals
•(gain electrons)
•No metallic luster
•Are not malleable
•Do not conduct
electricity
Metalloids
•B, Si, Ge, As, Sb, Te,
At
•Have properties
intermediate of metals
and non-metals
•Are semiconductors
Periodic Trends
Atoms get larger as go down a family group
Why? More energy levels and electrons, higher
energy levels are further from the nucleus
Atoms get smaller (diameter) as go across a period
(row).
Why? Greater positive pull on electrons and same
amount of shielding by inner electrons.
Ion Size
• The greater the net +
charge, the smaller the
ion
• The greater the net –
charge, the larger the
ion
Ionization Energy – the energy needed to
remove an electron
Li
Li+1 + eIonization energy = 8.64 x 10 -19 J/atom
Electron Affinity – the energy change that occurs when
an atom gains an extra electron.
The greater the negative number the greater the
electron affinity.
Complete Chapter
questions
• Pages 188-189 1-23, 25, 26, 29,
30, 33