Transcript Chapter-3-Periodic

Periodic table
Trends and patterns of properties
in the periodic table
• c
Organisation of the periodic table
(notes)
• The vertical columns of the table are
called groups or families. Element in the
same group have similar but not identical
characteristics
• Numbered from 1 to 18.
• Elements in the same
group have the same
number of outer shell
electrons, and hence similar chemical
properties.
Organisation of the periodic table
(notes)
• The horizontal rows of the table are called
periods.
• Numbered from 1 to 7.
• Each contains elements
with electrons in the same
outer shell.
The trends of the periodic table
• All elements in the same Group of the
Periodic Table
• have the same outer shell electron
configuration.
• All elements in the same Period of the
Periodic Table have outer shell electrons
• filling the same shell.
Types of elements
(notes)
• There are three main types of elements: metals, non
metals and metalloids
• 1. Metals appear on the left hand side of the zig zag
line that separates the periodic table
• 2. Non metals appear on the right hand side of the zig
zag line that separates the periodic table
• 3. Elements on either side of the zigzag line have
properties of both metals and non-metals. These
elements are called metalloids.
• x
Metals
• Most elements are metals. 88 elements to the left of the
stairstep line are metals or metal like elements.
• Left side of the periodic table
• Positive valencies
Physical Properties of Metals:
• Luster (shininess)
• Good conductors of heat and electricity
• High density (heavy for their size)
• High melting point
• Ductile (most metals can be drawn out into thin wires)
• Malleable (most metals can be hammered into thin sheets)
Chemical Properties of Metals:
• Easily lose electrons
• Corrode easily. Corrosion is a gradual wearing away.
(Example: silver tarnishing and iron rusting)
Non-metals
• Nonmetals are found to the right of the stairstep line.
Their characteristics are opposite those of metals.
Physical Properties of Nonmetals:
• No luster (dull appearance)
• Poor conductor of heat and electricity
• Brittle (breaks easily)
• Not ductile
• Not malleable
• Low density
• Low melting point
Chemical Properties of Nonmetals:
• Tend to gain electrons
• Since metals tend to lose electrons and nonmetals tend
to gain electrons, metals and nonmetals like to form
compounds with each other. These compounds are
called ionic compounds. When two or more nonmetals
bond with each other, they form a covalent compound.
Block Part of
Similarities in Elements
Periodic Table
s
Groups 1 and 2 Outer shell electrons are in
the s subshell (s1 and s2)
p
Groups 13 to 18 Outer shell electrons are in
the p subshell (s2p1 to s2p2)
d
Transition
metals –
Groups 3 to 12
Lanthanides
and Actinides
f
The d subshell is being
progressively filled (d1s2 to
d10s2)
The f subshell is being
progressively filled
Atomic properties
•
Many properties of atoms depend on the
strength of attraction between the outer
shell electrons and the nucleus
• This attraction will depend on
1. The positive charge that attracts the
other shell electrons
2. The distance of electrons from the
nucleus
In groups determine what will
happen to each of these properties
across a period and down a group
• Core Charge: The attraction that an outer shell
electron feels towards the nucleus
• Atomic Size: Diameter of an atom
• Ionisation Energy: Minimum amount of energy
required to remove the highest energy electron
from an atom (energy to steal an electron).
• Electronegativity: Measure of the ability of an
atom to attract an electron towards itself. (love
of electrons)
Core Charge
What is it?
• The attraction that an outer shell
electron feels towards the nucleus.
What happens down a group?
• Constant
• In the Alkaline metals there is always one
electron in the outer shell.
What happens across a period?
• Increases; there are more electrons in the
outer shell which are greatly attracted to the
nucleus.
• Lithium has one electron in its outer shell and
this is attracted to the protons in the nucleus.
The outer shell electron does not feel the full
attraction of the nucleus and therefore has a
core charge of +1
• Chlorine has 7 electrons in its outer shell
• What would its core charge be?
• Across a period the core charge changes
from +1 ,+ 2, +3, +4 etc.
Atomic Size or Radius
What is it?
• Diameter of atom
What happens down a group?
• Increases
• since there is an increase in the number of shells.
What happens across a period?
• Decreases
• since there is an increase in core charge, the outer
shell electrons are attracted closer to the nucleus
(it’s the same shell but there are more electrons in
the shell as you move across the period)
Atomic radius decreases across a period
• x
Atomic
radius
increases
down a
group
Trends in Ionisation energy
• The ionization energy is the amount of energy it
takes to detach one electron from a neutral atom
• Or How much energy it takes to steal an electron!!
• If its easy to steal a electron it has low ionisation
energy
• If its hard to steal an electron it has a high ionisation
energy
• The smaller the atom the harder to steal an electron
• The larger the atom the easier it is to steal an electron
e
Ionisation Energy
e
e
e
e
ee e
e
• What is it?
• Amount of energy required to
remove the highest energy electron
from an atom. (or steal one electron)
• What happens down a group?
• Decreases; since the size of the atom is
increasing, the attraction is weaker between the
outer shell electrons and the nucleus. Therefore
electrons are easier to remove.
• What happens across a period?
• Increases; since there is an increase in core
charge, the attraction is greater between the outer
shell electrons and the nucleus. Therefore
electrons are harder to remove.
• As the period begins it does not take a lot
of energy to remove an electron from Li
but as you go across the period it takes
more and more energy to take an electron
away
• b
Electronegativity
• http://www.youtube.com/watch?v=93G_Fq
pGFGY
• http://www.youtube.com/watch?v=dhEkyYUXSo
• http://www.youtube.com/watch?v=x4WEq
Wlp29U
Electronegativity
• What is it?
• Measure of the ability of an atom to attract an
electron towards itself or love of electrons!
• What happens down a group?
• Decreases; since the electrons are further from
the nucleus, there is a weaker attraction
• What happens across a period?
• Increases; since there is an increase in core
charge, there is a greater attraction of the outer
shell electrons to the nucleus.
e
• c
Reactivity of Metals
•
http://www.youtube.com/watch?v=GVoJZkmAAfA
(Group 1 in water)
• http://www.youtube.com/watch?v=V2TimLxskZw (Magnesium in water)
(Calcium in water)
• Group One (Alkaline Metals) are more
reactive than Group 2 (Alkaline Earths)
• As you go down a group metals become
more reactive
• This happens because as you go down a
group atoms get larger and metals tend to
donate electrons in reactions.
•
http://www.youtube.com/watch?v=nSgIr1Wba_g&feature=related
Reactivity of Non metals
• Look at table 3.3 to see which Halogen is
most reactive
• Reactivity decreases down the group
• Why? Think about atomic properties
• Non metals tend to form negative ions
(they gain electrons from other atoms)
• Electronegativity or love of electrons is
strongest with Fluorine and decreases
down the group.
Noble Gases
• Found in group 18 (the last column of the
periodic table.)
• Do not react easily with other elements, as
they have a full outer shell.
Homework
• Pg 51 Q 16 a and b, 18, 21, 22, 27