Ch.-5-Notes-Periodic-Table

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```					 The periodic table is
the most useful tool
in chemistry.
 You get to use it on
quizzes and tests!
 It organizes lots of
the known elements.
 …was a mess!!!
 No organization of
elements.
 Imagine going to a
grocery store with no
organization!!
 Difficult to find
information.
 Chemistry didn’t make
sense.
 Previous attempts to organize known elements failed
to work for all known elements at the time

 Russian Chemist and teacher, Dmitri Mendeleev,
discovered a way

 Found a way to approach the problem when playing
his favorite card game, a version of solitaire
(organization was the key)
 Solitaire…??????
HOW HIS WORKED…
 Put elements in rows by increasing atomic weight.
 Elements with similar properties were in the same
column.
 Put elements in columns by the way they reacted.
 Periodic Table: an arrangement of elements in
columns, based on a set of properties that repeat from
row to row
 Table was not complete, not all elements had yet been
discovered
   He left gaps/spaces in his table for those elements
   He was NOT the first to organize the elements in the
form of a table
   He was the FIRST to offer good explanations for how
the properties of an element were related to its
location in his table
   He used the gaps in his tables to predict properties of
undiscovered elements
   Other scientists used the predictions to help in their
search for undiscovered elements
 The close match between Mendeleev’s predictions
and the actual properties of new elements showed
how useful his periodic table could be
 With the periodic table, chemists could do more
than predict the properties of new elements – they
could explain the chemical behavior of different
groups of elements!!!
 Mendeleev wasn’t too far off.
 Now the elements are put in rows by increasing

ATOMIC NUMBER!!
 The horizontal rows are called periods and are labeled
from 1 to 7.
 The vertical columns are called groups are labeled
from 1 to 18.
 Period: A row in a periodic table of elements (left to
right)
 To understand the structure of the table, think what
happens as the atomic number increases:
 Reminder: Atomic Number = Number of Protons
 First energy level has ONLY 1 orbital
 The 1 e- in a hydrogen atom and 2 e- in a helium atom
can fit in this orbital (first energy level)
 This is why H and He are in Period 1
 Lithium, 1st element in Period 2, has one of its the
three electrons in the second energy level
 This is why lithium is the first element in Period 2
 Sodium, 1st element in Period 3, has one e- in its third
energy level
 Potassium, 1st element in Period 4, has 1 e- in its
fourth energy level
 This pattern applies to ALL the elements in the 1st
column on the table
 Columns are also grouped
into families (or groups).
 Families may be one
column, or several
columns put together.
 Families have names (Just
common last name.)
 Group: A column in a periodic table of elements
 Properties of elements repeat in a predictable
way when atomic numbers are used to arrange
elements into groups
 Periodic Law: the pattern of repeating properties
displayed by elements in the periodic table
 Elements within a group have similar properties:
 Similar e- configurations (see example above – first
column of the table)
 Electron configuration determines an elements
chemical properties
 Atomic mass is a value that depends on the
distribution of an element’s isotopes in nature and
the masses of those isotopes.
 Mass of an atom in grams is EXTREMELY small
 Scientists came up with an easier way to talk about
mass
 Chose one isotope to serve as a standard
 Scientists assigned 12 atomic mass units (amu’s) to the
carbon-12 atom (which has 6P and 6N)

 Atomic Mass Unit (amu): 1/12 the mass of a
carbon-12 atom
 Chlorine has an atomic number of 17 and an
atomic mass of 35.453 atomic mass units
 Where does the number 35.453 come from???
 There are two natural isotopes of Chlorine:
 Chlorine-35 which has 17 protons and 18 neutrons
 Chlorine-37 which has 17 protons and 20 neutrons
 Atomic masses come from an average of the
isotopes for a given element that exist in nature
 The value for atomic mass is known as a “weighted
average”

 Cl-35 occurs 3 times as often as Cl-37

 Take an average of those numbers:

(3 × 35) + (1 × 37)
-----------------------------   = 35.453
4
 Elements are classified as metals, nonmetals,
and metalloids.
 Metals: elements that are good conductors of electric
current and heat.
 Properties of Metals:
 Except for mercury, metals are solid at room
temperature
 Most metals are malleable
 Many metals are ductile (can be drawn into thin wires)
 Some metals are extremely reactive* (page 135, figure 10)
 *Meaning they easily combine chemically with other
elements
 Transition Metals: metals in groups 3-12, form a
bridge between the elements on the left and right
sides of the tables.
 Examples: copper and silver
 Some of the first elements discovered
 Ability to form compounds with distinctive colors
(page 137  production of colored glass)
 Includes the lanthanide and actinide series (at the
bottom of the table)
 Nonmetals: elements that are poor conductors of
heat and electric current
 Properties opposite those of metals
 Low boiling points
 Most are gases at room temperature
 Nonmetals that are solid at room temperature
tend to be brittle (will shatter)
 Some very reactive, some not at all, some fall
somewhere in between
 Fluorine (in Group 17) is the most reactive
nonmetal (found in toothpaste)
 Metalloids: elements with properties that fall
between those of metals and nonmetals
 Ability to conduct electric current varies with
temperature
 Pure silicon (Si) and germanium (Ge) are good
insulators at low temperatures and good conductors
at high temps.
 Across a period from left to right, the elements
become less metallic and more nonmetallic in their
properties
 Most reactive metals on left side
 Most reactive nonmetals on the right side (in Group 17)
 Period 3 elements (left to right) provide an example of
this (page 138, Figure 13)
 Why is hydrogen (H)
on the left side of the
table with the active
metals?
 Hydrogen’s location is
related to its electron
configuration, not its
properties!!!
 Wonder why there are 2 numbering schemes on the
periodic table?
 When the ‘A’ groups are numbered 1-8, they provide a
reminder about the electron configurations of the
elements in those groups
 The number of an ‘A’ group matches the number of
valance electrons in an electron configuration for an
element in that group
 Valence Electron: an electron that is in the highest
occupied energy level of an atom
 Valence electrons play a key role in chemical reactions
 Properties vary across a period because the number of
valence electrons increases from left to right
 Elements in a group have similar properties because
they have the same number of valence electron
 Hydrogen is on far left of table because it has one
valence electron, just like the rest of the elements in
that column
 Hydrogen belongs to a
family of its own.
   Hydrogen is a diatomic,
reactive gas.
   Hydrogen was involved
in the explosion of the
Hindenberg.
/watch?v=F54rqDh2mW
A
   Hydrogen is promising as
an alternative fuel source
for automobiles.
 1st column on the periodic table (Group 1
/1A) not including hydrogen.
 Very reactive metals, always combined
with something else in nature (like in
salt).
 Single valence electron
 Soft enough to cut with a butter knife.
 The reactivity of alkali metals increases from the
top of Group 1A to the bottom
 Lithium (Li) down through Francium (Fr)

 Group 2 / 2A on the periodic table.
 Reactive metals that are always
combined with nonmetals in
nature.
 Several of these elements are
important mineral nutrients (such
as Mg and Ca).
 2 valence electrons
 Harder than metals in Group 1A
 Higher melting point than Group 1A
 Differences in reactivity among the alkaline earth
metals are shown by the ways they react with water
 Calcium, strontium, and barium react easily with
cold water
 Magnesium reacts with hot water
 No change with beryllium and water
 Elements in groups 3-
12
 Less reactive, harder
metals.
 Includes metals used
in jewelry and
construction.
 Most are hard and
shiny.
 Elements in group 13 (3A)
 Aluminum:
 Metal was once rare and expensive,
not a “disposable metal.”
 Most abundant metal in Earth’s
crust
 Less reactive than sodium and
magnesium
 strong, lightweight, malleable, and
good conductor of electric current
 3 valence electrons
 Boron is used in
because it doesn’t shatter
when it undergoes a rapid
temperature change
 Elements in group 14 (4A)
 Group 4A contains one nonmetal (C), 2
metalloids (Si, Ge), and 2 metals (Sn,
Pb)
 Contains elements important to life and
computers.
 Carbon is the basis for an entire branch
of chemistry.
 Coal and oil are mostly made of carbon.
 4 valence electrons
 Metallic nature increases from top to bottom (Ge is
better conductor than Si)
 Life would not exist without carbon (except for
water, most of the compounds in your body contain
carbon)
 Reactions in your body controlled by carbon
compounds
 Si is 2nd most abundant element in Earth’s crust
(found in rocks, sand, and glass)
 Elements in group 15 (5A)
 Nitrogen makes up over ¾ of
the atmosphere.
 Nitrogen and phosphorus are
both important in living
things.
 The red stuff on the tip of
matches is phosphorus.
 5 valence electrons
 2 nonmetals, 2
metalloids, and 1 metal
 Contain a wide range of
physical properties
 Elements in group 16 (6A)
 Oxygen is necessary for
respiration.
 Many things that stink,
contain sulfur (rotten
eggs, garlic, skunks, etc.)
 6 valence electrons
 3 nonmetals and 2 metalloids
 Oxygen is most abundant element in Earth’s crust

The 10 most
abundant elements
by mass in the
earth's crust . All
are main-group
elements except
iron and titanium.
 Elements in group 17 (7A)
 Very reactive, volatile,
diatomic, nonmetals
 Always found combined
with other element in
nature .
 Used as disinfectants and
to strengthen teeth.
 7 valence electrons
 Despite physical differences, the halogens have similar
chemical properties
 Highly reactive nonmetals, with fluorine being the
most reactive and chlorine a close 2nd
 React easily with most metals
 Chlorine added to drinking water and swimming
pools to kill bacteria
 Elements in group 18 (8A)
 VERY unreactive,
monatomic gases
 Used in blimps to fix the
Hindenberg problem.
 Have a full valence shell.
 8 valence electrons
 EXCEPTION is Helium, it has 2 valence electrons
 Colorless and odorless
 Used in lighted “neon” signs

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