Download The Periodic Table - TangHua2012-2013

The Periodic Table
The Old Table
• 1869 – Mendeleev:
method of organizing
the elements
according to both
their masses and
their properties.
• Vertical Columns: Elements arranged in
groups each group shares similar
properties.
• Horizontal Rows: Elements are arranged
in periods
Mendeleev’s table showed gaps,
indicating missing elements (not
discovered yet). Why was this important?
• The location of missing elements allowed their
chemical and physical properties to be
predicted.
The Modern Periodic Table
• Elements arranged by atomic number
(not mass)
• (eg. K heavier than Ar…..due to isotopes)
Periodic Law:
“The properties of the elements recur along the
rows” (i.e. an element has similar properties to
the one below or above it)
Division in the Periodic Table
• Period: all elements in a given row of the
periodic table.
• Group or family: all elements in a given
column of the periodic table.
Rows = Periods
Columns = Groups or families
Particular groups, rows and blocks of elements
Alkali metals
group 1 (except hydrogen)
Alkaline earth metals
group 2
Transition metals
block d
Representative
elements
Halogens
main group elements, s and p blocks
2nd last group (starts with F)
Noble gases
last group (these elements have full valence
orbitals)
Lanthanides
row with atomic # 57 → # 71
Actinides
below Lanthanides, atomic # 89 → #103
We can also divide P.T. into: Metals, Non-metals
and Semiconductors
• Elements become more __metallic______
from _right___ to __left_____ across the
periodic table and from ___top_____ to
_bottom__ of a group.
Properties of METALS:
•
•
•
•
•
•
shiny.
opaque.
good conductors of heat and electricity.
usually flexible when in sheet form.
malleable and ductile.
solid at room temp. (except of Hg)
Properties of NON-METALS:
• gas, liquid, or brittle solids at room temp.
• poor conductors of heat and electricity.
• solids are not shiny
2 types of Non- metals:
• 1. Low electrical conductivities.
• 2. Moderate electrical conductivities.
Some elements DO share properties
of metals and non-metals
Semiconductors (metalloids or moderate
electrical conductivities )
• non-metal.
• electrical conductivity increases when ↑T
• eg) B, Si, Ge, As, Sb, Te, At
Now You Try!!
• Do the following questions with your
partner orally (5 min)
Homework p. 164
#35-39
Electrostatic Trends in P.T.
•
from right to left and top to bottom of the Periodic Table
– elements become more metallic
– atomic radius increases
•
from left to right and bottom to top of the P.T
– electron affinity increases
– ionization energy increases
– Electronegativity increases
Electronegativity
Electronegativity
Ionization Energy (I.E.)
• I.E. is the energy required to remove one or more
electrons from a neutral atom in the gas phase
•
•
•
•
1st I.E.: The energy required to remove the 1st valence electron
2nd I.E.: The energy required to remove the 2nd valence electron
3rd I.E.: The energy required to remove the 3rd valence electron
4th I.E.: The energy required to remove the 4th valence electron
eg)
1st IE: Rb(g)  Rb+(g) + e2nd IE: Rb+ (g)  Rb2+ (g) + e3rd IE: Rb2+(g)  Rb 3+ (g) + e-
(∆Hº = 400 kJ/mol)
(∆Hº = 580 kJ/mol)
(∆Hº = 600 kJ/mol)
Explaining I.E.’s
1. The positively charged nucleus attracts
the electrons therefore the 1st I.E. of He
is approx twice the 1st I.E. of H. This is
because H has 1 proton and He has 2.
Therefore the IE increases as nucleus
size increases
2. Electrons in higher n feel less attraction to
the nucleus because electrons in smaller n
shield/block the attractive force of nucleus
electrons in higher n are easier to remove.
Therefore IE decrease as n increases.
eg) Which has higher I.E.?
a. Na
b. Mg
c. F
or
or
or
Mg
Al
Cl
Now You Try
• Do these questions
• p. 168 #48, 49 and 51
Electron Affinity (E.A.)
• E.A. is the ∆E that occurs when a neutral atom
in the gas phase gains an electron.
(or how much a neutral atom wants an
electron)
eg) F (g) + e-  F- (g)
E.A. increases as atom size decreases because
the elecrons added is nearer the nucleus (lower n)
the electrons repelled by fewer other electrons
Atomic Radius
•
Atomic radius: distance from
center of nucleus to
outermost electron
1)
Moving down a group,
•
•
•
2)
n increases
orbital size increases
atomic radius increases
Moving left to right across a period
–
–
–
Number of protons increases
orbital size decreases
atomic radius decreases
eg) Which is smaller?
•
•
•
•
a)
b)
c)
d)
K
Rb
Sn
O
or
or
or
or
Ca
Sb
Pb
S
Now you try!!
• Do these questions in your work book
• P. 170-171 # 53(a,b,c,d,f) 54, 55(a,b,c,d,f) 56
Electronegativity (E.N.)
• E.N. is the tendency of the
atom to attract e-s from a
neighbouring atom or how
strongly an atom pulls on
nearby electrons.
• E.N. increases as you move
from left to right () and from
bottom to top(↑) of the P.T.
Atoms with high Electronegativity
• strongly attracts e-s from nearby atoms
• strongly attracts its own valence e-s
vice versa also true…..
• Atoms with low E.N.
– have little attraction for electrons from a
nearby atom and for its own electrons
• eg) Li and F
• Li has low E.N. \gives away an e- easily)
• F has high E.N. \attracts e- strongly)
• If F and Li are near F takes an e- from Li
In the P.T:
Moving:
Atom’s properties are affected by:
Down a family…
Increasing atom size and increasing
distance between nucleus and
valence e-s
Across a period….
Differing valence, nuclear charge,
and charge on species
Chemical Reactivity
• How likely or strongly an atom will react
with other substances. This is determined
by how easily electrons can be removed
(ionization energy) and how badly they
want to take other atom's electrons
(electronegativity).
Metals
• Period - reactivity decreases as you go
from left to right across a period.
• Group - reactivity increases as you go
down a group
• Why? The farther to the left and down the
periodic chart you go, the easier it is for
electrons to be given or taken away,
resulting in higher reactivity.
Non-metals
• Period - reactivity increases as you go
from the left to the right across a period
• Group - reactivity decreases as you go
down the group.
• Why? The farther right and up you go on
the periodic table, the higher the
electronegativity, resulting in a more
vigorous exchange of electrons.
Exception
• Nobel gases are non reactive
Now you try!!
• Do these questions in your work book
p. 173 #58 – 61