Download UNIT 5 RECOVERED

The Periodic Table
Unit 5
Ion
• Cation – when an atom
loses an electron, positive
atom after losing an electron.
• Metals become cations.
• Anion – when an atom gains an
electron, negative atom after gaining
an electron.
• Nonmetals become anions.
Mendeleev
• First scientist to organize a periodic table of
elements.
Mendeleev’s ptable
Why is the Periodic Table important
to me?
• The periodic table is
the most useful tool
to a chemist.
• You get to use it on
every test.
• It organizes lots of
information about all
the known elements.
Pre-Periodic Table Chemistry …
• …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.
Dmitri Mendeleev: Father of the Table
HOW HIS WORKED…
• Put elements in rows by
increasing atomic
weight.
• Put elements in
columns by the way
they reacted.
SOME PROBLEMS…
• He left blank spaces for
what he said were
undiscovered elements.
(Turned out he was
right!)
• He broke the pattern of
increasing atomic
weight to keep similar
reacting elements
together.
The Current Periodic Table
• 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.
Groups…Here’s Where the Periodic
Table Gets Useful!!
• Elements in the
same group
have similar
chemical and
physical
properties!!
• (Mendeleev did that on
purpose.)
Why??
• They have the same
number of valence
electrons.
• They will form the same
kinds of ions.
Families on the Periodic Table
• Columns are also grouped
into families.
• Families may be one
column, or several
columns put together.
• Families have names
rather than numbers.
(Just like your family has a
common last name.)
Hydrogen
• Hydrogen belongs to a
family of its own.
• Hydrogen is a diatomic,
reactive gas.
• Hydrogen was involved in
the explosion of the
Hindenberg.
• Hydrogen is promising as
an alternative fuel source
for automobiles
Alkali Metals
• 1st column on the periodic table
(Group 1) not including hydrogen.
• Very reactive metals, always
combined with something else in
nature (like in salt).
• Soft enough to cut with a butter
knife
• https://www.youtube.com/watch
?v=cqeVEFFzz7E
Alkaline Earth Metals
• Second column on the
periodic table. (Group
2)
• Reactive metals that are
always combined with
nonmetals in nature.
• Several of these
elements are important
mineral nutrients (such
as Mg and Ca
Transition Metals
• Elements in groups 312
• Less reactive harder
metals
• Includes metals used
in jewelry and
construction.
• Metals used “as
metal.”
Boron Family
• Elements in group 13
• Aluminum metal was
once rare and
expensive, not a
“disposable metal.”
Carbon Family
• Elements in group 14
• Contains elements
important to life and
computers.
• Carbon is the basis for
an entire branch of
chemistry.
• Silicon and
Germanium are
important
semiconductors.
Nitrogen Family
• Elements in group 15
• Nitrogen makes up over
¾ of the atmosphere.
• Nitrogen and
phosphorus are both
important in living
things.
• Most of the world’s
nitrogen is not available
to living things.
• The red stuff on the tip
of matches is
phosphorus.
Oxygen Family or Chalcogens
• Elements in group 16
• Oxygen is necessary
for respiration.
• Many things that
stink, contain sulfur
(rotten eggs, garlic,
skunks,etc.)
Halogens
• Elements in group 17
• Very reactive, volatile,
diatomic, nonmetals
• Always found
combined with other
element in nature .
• Used as disinfectants
and to strengthen
teeth.
The Noble Gases
The Noble Gases
• Elements in group 18
• VERY unreactive,
monatomic gases
• Used in lighted “neon”
signs
• Used in blimps to fix the
Hindenberg problem.
• Have a full valence shell.
• https://www.youtube.co
m/watch?v=1y0zhWp_4S
w
Section A: Complete the chart using a periodic table to help you.
Answer these questions:
An atom that gains one or more electrons will have a ____________________
charge.
An atom that loses one or more electrons will have a ____________________
charge.
An atom that gains or loses one or more electrons is called an ____________.
CATION and a negative ion is called an
A positive ion is called a ______________
ANION
_______________.
“Cat-Eye-On”
“An-Eye-On”
What is an ionic bond?
Atoms will transfer one or more ________________
ELECTRONS to another to form the bond.
COMPLETE outer shell.
Each atom is left with a ________________
An ionic bond forms between a ___________
METAL ion with a positive charge and a
________________
NONMETAL ion with a negative charge.
Example B1: Sodium + Chlorine
Example B2: Magnesium + Iodine
Atomic Radius
• Measured from nucleus to outermost
electron.
• Unit commonly used is pm
• picometer= 10-12m
• Example: iodine atomic radius 140pm
How does atomic radius change across a
period?
• It is smaller to the right.
• Why?
• More protons in the nucleus higher
electrical force pulls electrons closer to
nucleus. – makes atom more tightly smaller.
How does atomic radius change down a
group?
• It is larger down the group.
• Why?
• Valence electrons are at higher energy levels
and are not bound as tightly to the nucleus
because they are screened or shielded (
pushed away) by other electrons in inner
levels.
The Periodic Table and Atomic Radius
Example:
Which is larger: a lithium atom or a fluorine
atom?
A lithium atom
Example:
• Which is larger: an arsenic atom or a sulfur
atom?
• An arsenic atom
Ionization energy
• Ionization energy is the amount of energy
needed to remove an electron from an atom.
Ion
• Positive ion ---removal of electron
• CATION
• Negative ion--- addition of electron
• ANION
How does ionization energy change down a
group?
• The ionization
energy decreases
as you move down
a group.
• Why?
– The size of the
atom increases.
– Electron is further
from the nucleus.
– Easier to take
electrons.
How does ionization energy change across
a period?
• The ionization energy increases as you move
from left to right across a period.
• Why?
– Nuclear charge because the atomic number
increases.
– Attraction of the electron to the nucleus
increases.
Ionic size
• Metallic elements easily lose electrons.
• Non-metals more readily gain electrons.
How does losing or gaining an electron effect
the size of the atom (ion) ?
Positive ions
• Positive ions are always smaller than the
neutral atom. Loss of outer shell electrons.
Negative Ions
• Negative ions are always larger than the
neutral atom. Gaining electrons.
Electronegativity: the ability of an atom
in a bond to pull on the electron. (Linus
Pauling)
Electronegativity
• When electrons are shared by two atoms a
covalent bond is formed.
• When electrons are transferred from one
atom to another an ionic bond is formed.
• When the atoms are the same they pull on the
electrons equally. Example, H-H.
• When the atoms are different, the atoms pull
on the electrons unevenly. Example, HCl
Trends in Electronegativity
• Electronegativity generally decreases as you
move down a group.
• Electronegativity of the representative elements
(Group A elements/not transition) increases as
you move across a period.
Electronegativities of Some Elements
Element
F
Cl
O
N
S
C
H
Na
Fr
Pauling scale
4.0 highest possible #
3.0
3.5
3.0
2.5
2.5
2.1
0.9
0.7 lowest
Note
• Most electronegative element is F
(EN 4.0)
• Least electronegative stable element is Cs
(EN 0.7)
Review
Ionization Energy
Electronegativity
Amount of energy needed The ability for an atom to
to take an electron from
gain an electron.
an atom.
Nonmetals do not like to
give up electrons. HIGH
Nonmetals like to take
electrons. HIGH
• https://www.youtube.com/watch?v=mlRhLicN
o8Q
• Naming ions and acids