Transcript Periodic Table and Trends

Periodic Table and Trends
Organization of the Periodic Table
First created by Dmitri
Mendeleev
1.
A.
B.
Organized atoms by
atomic masses
This was ok, but trends
in the periodic table did
not match up
A.
Mendeleev was able to predict how elements
interacted with each other and wanted his table
to display those trends.
Henry Moseley
1.
2.
Took the nuclear
charge, which is the
number of protons in
the nucleus, and
ordered the periodic
table using the
number of protons in
the atom.
The trends found by
Mendeleev were in
place.
Periodic Law
States that physical and chemical properties
of elements are properties of their atomic
number.
Each column on the periodic table is called
a group
1.
2.
A.
Groups have the same number of electrons in
their outer-most sublevel
3.
4.
Each row in the periodic table is called a
period
Elements in the same period share the
same energy level.
Noble Gases
Noble Gases
Group 8A
Have filled s and p orbitals
Are very stable. Do not form bonds with
other molecules
All atoms desire to be noble gases and will
give or take electrons from other atoms to
do so.
1.
2.
3.
4.
A.
This is how a compound/molecule is made
5.
To act like noble gases, atoms will take the
easiest route, and either give up electrons
or gain them
Alkali Metals
Alkali Metals
Found in Group 1A
Made of soft metals (meaning easy to bend)
Outer electron shell has an s1 configuration
React quickly with water or air
1.
2.
3.
4.
A.
Can create a basic solution with water
Have an extra electron to give up in order to form a
+1 ion.
[why is it +1? If you look at Li, Li has 3 protons, so it
must have 3 electrons. To get to the nearest noble
gas, helium, Li would have to lose 1 electron.
5.
Alkaline Earth Metals
Alkaline Earth Metals
1.
2.
3.
4.
Group 2A
Outershell has a s2 configuration
Metals are harder and less reactive
Become ions with a +2 charge
Transition Metals
Transition metals
1.
2.
Groups 3B-12B
Harder metals and even less reactive than
groups 1 and 2
Lanthanides
Lanthanides
Contain atomic numbers 57-71
2. Shiny and reactive metals
3. Some glow when electrons hit them.
[europium]
4. 4f series
1.
Actinides
Actinides
5f series
All are radioactive
1.
2.
A.
B.
Uranium important for nuclear reactions
Many are man-made
Main Block Elements
Groups 3A-8A
Made of metals, metalloids, and nonmetals
1.
2.
A.
B.
C.
Metal examples: aluminum, gallium, indium, tin
thallium, lead, bismuth, polonium
Metalloids: boron, silicon, germanium, arsenic,
antimony, and tellurium.
Nonmetal examples: hydrogen, oxygen,
nitrogen, carbon, phosphorus, sulfur, selenium,
fluoride, chlorine, bromide, iodine, and noble
gases
The periodic stair step: The area on the
periodic table that divides the metals from
the nonmetals
3.
Atoms around the stair step are metalloids
A.
i.
ii.
Metalloids have characteristics of nonmetals and
metals
Metalloids are also termed semiconductors
Halogens
Halogens
Group 7A
Form salts with group 1 metals
The most reactive nonmetals
Gain electrons to have a noble gas
configuration
1.
2.
3.
4.
A.
Become a -1 ion if this happens
Chalcogens
Group 6A
Try to gain two electrons to have a noble
gas electron configuration.
1.
2.
A.
Become a -2 ion if this happens
Periodic Trends
The four different trends to know include:
1.
A.
B.
C.
D.
Electronegativity
Atomic radius
Electron affinity
Ionization energy
Electronegativity
1.
2.
3.
Defined by an atoms tendency to attract
electrons in a chemical bond.
In a chemical bond, atoms have to share
electrons
The atom with a higher electronegativity will
keep the electrons closer to it.
Atoms with the highest electronegativity are
found in the upper, right-side of the periodic
table; excluding noble gases.
The atom with the highest electronegativity
is fluorine
4.
5.
A.
The lowest is francium
Atomic Radius
Atoms with the largest atomic radius are
found at the bottom, left-side of the periodic
table
why?
2. The further you go down the periodic table,
the more energy levels an atom contains.
1.
A.
This means, assuming the atom looks like a
sphere, the radius of the atom would increase as
you go down the periodic table.
3.
4.
5.
The top, right-area of the periodic table has
the smallest atomic radius (helium)
Which would you assume to have the
largest atomic radius: Al, Al+, or AlWhich would you assume to have the
smallest atomic radius: C2+, C+, C, C-, C2-
Ranking Elements by Atomic Size
PROBLEM:
Using only the periodic table, rank each set of main group
elements in order of decreasing atomic size:
(a) Ca, Mg, Sr
PLAN:
(b) K, Ga, Ca
(c) Br, Rb, Kr
(d) Sr, Ca, Rb
Elements in the same group increase in size as you go down;
elements decrease in size as you go across a period.
SOLUTION:
(a) Sr > Ca > Mg
These elements are in Group 2A(2), and size
decreases up the group.
(b) K > Ca > Ga
These elements are in Period 4, and size
decreases across a period.
(c) Rb > Br > Kr
Rb has a higher energy level and is far to the left.
Br is to the left of Kr in Period 4.
(d) Rb > Sr > Ca
Ca is one energy level smaller than Rb and Sr.
Rb is to the left of Sr in the same period.
Ionization Energy
1.
2.
3.
Defined as the energy needed to remove an
electron from an atom
The top, right-area of the periodic table
contains the atoms with the highest
ionization energy.
Helium has the highest ionization energy.
Ranking Elements by First Ionization Energy
PROBLEM:
Using the periodic table only, rank the elements in each of the
following sets in order of decreasing IE1:
(a) Kr, He, Ar
PLAN:
(b) Sb, Te, Sn
(c) K, Ca, Rb
(d) I, Xe, Cs
IE decreases as you proceed down in a group; IE increases as
you go across a period.
SOLUTION:
(a) He > Ar > Kr
These three elements are all in Group 8A(18), IE
decreases down a group.
(b) Te > Sb > Sn
These are all in Period 5, IE increases across a
period.
(c) Ca > K > Rb
Ca is to the right of K; Rb is below K.
(d) Xe > I > Cs
I is to the left of Xe; Cs is further to the left and
down one period.
Electron Affinity
1.
2.
3.
The ability of an atom to attract and hold
onto an atom.
Electron affinity is highest in the upper,
right-area of the periodic table.
Fluorine has the highest electron affinity.
Shielding effect: inner electrons are
shielding the pull of the nucleus, so outer
electrons are removed before inner
electrons.
4.
A.
B.
That is why Francium is so reactive. It quickly
reacts with something around it.
Electrons in the outer energy levels feel less of
the nuclear charge (they feel less of the positive
charge).