Title: The Periodic Table
1Emma Jones
The Periodic Table
2The modern periodic table. The periods are the
horizontal rows. The blue-shaded elements may be
omitted.
3- The modern periodic table has the elements
arranged in order of increasing atomic number. - A vertical column, called a group, contains
elements with similar properties. - A period runs from left to right with the atomic
number of the elements increasing from left to
right. - The zig-zag red line shows the boundary between
metals (on the left) and non-metals.
4Alkali Metals
- Group 1 is the vertical column on the far left of
the periodic table. - You can probably see lithium, sodium and
potassium as a demonstration as they are the
least reactive, but rubidium and caesium are
considered to be too reactive to demonstrate. - Francium is radioactive, very rare and the most
reactive element in group one.
5Group one elements is shaded blue
- The common properties of Group one/Alkali Metals
is that - They have low melting and boiling points compared
to most other metals in the periodic table. - They are very soft and can be cut easily with a
knife. - They have low densities as lithium, sodium and
potassium will float on water whereas the other
elements will not - They react quickly with water, producing
hydroxides and hydrogen gas.
6Melting points
- The alkali metals have low melting and boiling
points compared to most other metals. - You can see from the graph that lithium, at
the top of Group 1, has the highest melting point
in the group.
7Density
- The density of a substance is a measure of how
heavy it is for its size. - The alkali metals have low densities
(measured in grams/cubic centimetre) compared to
most other metals. - As you can see from the table that lithium
has the lowest density in the group.
8Trends in Chemical Properties
- As well as knowing that alkali metals become more
reactive as you go down the group.
Lithium and waterThis is the equation for the
reactionlithium water       lithium
hydroxide hydrogen 2Li(s) 2H2O(l) Â Â Â Â Â
2LiOH(aq) H2(g)When added to
water, lithium floats. It fizzes steadily and
becomes smaller until eventually it disappears.
9Sodium and waterThis is the equation for the
reaction sodium water     sodium
hydroxide hydrogen2Na(s) 2H2O(l) Â Â Â Â
 2NaOH(aq) H2(g)When added to water, sodium
melts to form a ball that moves around on the
surface. It fizzes rapidly, and may set on fire
with an orange flame before disappearing.
Potassium and waterThis is the equation for the
reactionpotassium water     potassium
hydroxide hydrogen2K(s) 2H2O(l) Â Â Â Â
2KOH(aq) H2(g)When added to water, potassium
floats. It reacts so quickly that it sets on
fire with sparks and a lilac flame, and explodes
at the end of the reaction.
10Group 7 The Halogens
- The elements in Group 7 are called halogens.
They belong to the column second from right in
the periodic table.The halogens are non-metals
with molecules that each contain two atoms. They
have low melting points and boiling points, and
they also form coloured vapours. They are poor
conductors of heat and electricity. - Group 7 is the vertical column second from right
in the periodic table. Fluorine is far too
dangerous to handle at school but you will
probably see chlorine and iodine there. Bromine
is a hazardous liquid but you may see a weak
solution of it. Astatine is radioactive and very
rare there are only a few grams of it in the
whole of the Earth's crust at any time.
11Group 7 elements is the shaded blue
- The common properties of the Halogens are
- They are non-metals.
- They have low melting and boiling points.
- They are poor conductors of heat and electricity.
- They have coloured vapours.
- Their molecules each contain two atoms (they are
diatomic).
12Melting point and boiling point
- The halogens have low melting points and boiling
points. - This is a typical property of non-metals.
- You can see from the graph that fluorine, at the
top of Group 7, has the lowest melting point and
boiling point in the Group.
13State at room temperature
- Room temperature is usually about 20C. At
this temperature, fluorine and chlorine are
gases, bromine is a liquid, and iodine and
astatine are solids. - Remember this trend as top two elements are
gases, the bottom two are solids and the middle
element is liquid.
Colour
The halogens become darker as you go down the
group. Fluorine is very pale yellow, chlorine is
yellow-green and bromine is red-brown. Iodine
crystals are shiny purple-black but easily turn
into a dark purple vapour when they are warmed
up.
14Trends in Chemical PropertiesReactions with
Metals
- The halogens react with metals to make salts
called metal halides. For example, sodium reacts
with chlorine to make sodium chloride (common
salt)sodium chlorine   sodium chloride - metal halogen metal halide
Sodium chloride is an ionic salt. It contains
sodium ions and chloride ions. Chloride ions
have a -1 charge. You will have come across
compounds containing fluoride ions in, for
example toothpaste.
15Reactions with Hydrogens
- The halogens react with hydrogen to make
molecular compounds called hydrogen halides.
These dissolve in water to form acidic solutions.
For example, hydrogen reacts with chlorine to
make hydrogen chloridehydrogen chlorine Â
hydrogen chloridehydrogen halogen hydrogen
halideHydrogen chloride dissolves in water to
make the familiar laboratory chemical,
hydrochloric acid.
Trend in reactivityThe halogens become less
reactive as you go down the group. Fluorine, at
the top of the group, is the most reactive
halogen. It is extremely dangerous and will even
attack glass. Iodine, near the bottom of the
group, is much less reactive and is used as an
antiseptic.
16Halogen displacement reactions
- Remember that a more-reactive halogen can
displace a less-reactive halogen from its salt
dissolved in water. Here's an example - Displacement of bromine from sodium
bromideChlorine is more reactive than bromine
(you know this because chlorine is above bromine
in Group 7). Sodium bromide is a salt of bromine
that will dissolve in water. So chlorine will
displace bromine from sodium bromide solution. - This means that if chlorine (as a gas or
dissolved in water) is added to sodium bromide
solution, bromine forms and the mixture turns
brown. We say that bromine has been displaced
from sodium bromide. Displaced is just a
chemist's word for pushed out. The equation for
the reaction is
chlorine sodium bromide -Â Â Â sodium chloride
bromineCl2(aq) 2NaBr(aq) -
2NaCl(aq) Br2(aq)
17- You can see that the Cl and Br have swapped
places. - If you test different combinations of the
halogens and their salts you can work out a
reactivity series for Group 7. - The most reactive halogen displaces all the
other halogens from solutions of their salts,
while the least reactive halogen is always
displaced. - It works just the same whether you use a
sodium salt or a potassium salt.