Group-VII (halogens)
elements:
F
Cl
Br
I
At
Molecular formula, colourand Physical state of halogens:
Halogen molecules colour Physical state
F2 Pale yellow gas
Cl2 Pale green gas
Br2 red brown liquid
I2 grey-black solid
Diatomic molecules:
A molecule that is made up of only two atoms is called diatomic molecules.
Examples: Molecules Formula
Flourine F2
Chlorine Cl2
Bromine Br2
Iodine I2
Hydrogen H2
Oxygen O2
Nitrogen N2
Assessment
1. A molecules that is made up of only two atoms is called ……………. molecules.
a. Diatomic b. mono atomic c. triatomic
2. Fluorine gas exist in ………….. State.
a. Solid b. gas c. liquid
3. Chlorine element belongs to group …………?
a. 1 b. 6 c. 7
Physical properties of Halogens:
1-Halogens exist in three physical states solid, liquid and gas.
2-They have low melting point(m.p) and boiling point (b.p)
3-They have low density.
4-They do not conduct electricity.
Monoatomic & triatomic molecules:
Mono atomic molecule:
Noble gases are called mono atomic molecules because they consist of only one atom. E.g. He, Ne, Ar etc
Tri atomic molecules:
The molecules that consist of three atoms are called triatomic molecules. E.g. H2O, CO2, O3etc.
Assessment
1.
The molecules that consist of three atoms are called …….. Molecules?
a. Mono atomic b.. Diatomic c. triatomic
2.Halogens do not conduct electricity?
a. True b. false c. none
3. Noble gases are called mono atomic molecules because they consist of only …………. Atom?
a. One b. two c. three
Chemical properties of Halogens:
1) Reaction of halogens with water:
When halogens react with water, a mixture of acids is formed.
e.g,Aqueoussolution of Chlorine acts as a Bleach.
Cl2+ H2O HCl+ HOCl
(Hydrochloric acid) (Hypochloricacid)
2) Reaction of Halogen with metals:
Halogens react with metals to form salts.
e.g, 2Na + Cl22NaCl
2Fe + 3Cl22FeCl3
3. Reaction of Halogens with hydrogen gas:
Halogen react with H2gas to form acids.
e.g, Cl2+ H22HCl
Br2+ H22HBr
(hydrogen bromide)
Assessment
1. Aqueous solution of Chlorine acts as a ……….?
a. Catalyst b. Enzyme c. bleach
2. Halogens react with metals to form …………..?
a. Acid b. Base c. Salt
3. Halogen react with H2gas to form …………?
a. Acid b. Base c. Salt
4. 2Na + Cl2………….. ?
a. 2NaCl b. NaCl c. NaCl2
Displacement reaction:
It is a type of reaction in which more reactive element displaces the less reactive element from its compound.
Example: Chlorine is more reactive than iodine or bromine. It can ‘push’ (displace) bromide and iodide out of solution.
Chlorine + Potassium Bromide Potassium Chloride + Bromine
(word equation)
Cl2+ 2kBr 2kCl + Br2
(aq) (aq) (aq) (aq)
(Symbolic equation)
Periodic trend of the Properties of halogens:
1)
Reactivity of halogens decreases down the group.
Most reactive F
Cl
BrReactivity
Least reactiveI
2) m.pand b.pof halogens increases down the group.
3) Density of halogens increases down the group.
4)Colourof halogens becomes darker down the group.
Assessment
1. Reaction in which more reactive element displaces the less reactive element from its compound are called…….?
a. Displacement reaction b. Active reaction c. Atom
2. Density of halogens increases ………. the group?
a. Down b. Up c. none
3.Reactivity of halogens ……………. down the group?
a. Increases b. Decreases c. Stable
ClassWorkUses of Flourine:
i)
It is used in tooth-paste to prevent the tooth decay.
ii)
Teflon is flourinecompound that is used in non-sticky pans.
Uses of Chlorine:
Chlorine and its compounds have many uses:
1) Solvents
2) Killing bacteria in swimming pools.
3) Antiseptic and disinfectants.
4) Bleach to kill bacteria and to whiten paper
5) In making hydrochloric acid.
Noble gases:
Group-VIII elements are called Noble gases or inert gases.
Noble gases are also called monoatomic gases.
Noble gases so unreactive (inert):
Noble gases are unreactive (stable) because their outermost shells are completely full of electrons.
e.g, He
1stShell = 2e-
e.g, Ne
1stshell = 2e-
2ndshell = 8e-
Class Assessment
1.Noble gases are unreactive (stable) because their outermost shells are …………. full of electrons?
a. Partially b. completely c. Ionic
2. Group-VIII elements are called ………….. gases?
a. Noble b. halogen c. alkali
3. …………. is used in Killing bacteria in swimming pools?
a. Flourineb. Chlorine c. Bromine
Uses of Helium: (He)
i) It is used in air ships(weather balloon).
ii) It is used in body scanner (instrument).
Uses of Neon: (Ne)
i) It is used in red signs (e.g. traffic signals)
Uses of Bromine:
i) It is used in pesticides.
ii) It is used to make medicine.
iii) It is used in photo graphic film.
Uses of Iodine:
Iodine is used in antiseptics.
Uses of Ar:
i) It is filled in the light bulbs
ii) It provides inert atmosphere in welding.
iii) It is used in the extraction of Titanium (Ti) metal.
Uses of Radon:
Radon is radioactive and is used to treat cancer.
Uses of Krypton:
It is used in laser to operate eye.
Assessment
1 .…………… is used in air ships(weather balloon).
a. Helium b. Argon c. Bromine
2. …………… is used in red signs (e.g. traffic signals).
a. Chlorine b. Neon c. Iodine
3. ………….. is radioactive and is used to treat cancer.
a. Radon b. Argon c. Uranium
4. …………. is used in laser to operate eye.
a. Polonium b. Iron c. Krypton
Group-VIIGroup-VIII
elements:
He
Ne
Ar
Kr
Xe
Rn
Atomic structure and the Periodic Table
elements in the Periodic Table are arranged in order of atomic number. (number of protons in an atom)
The atoms of each element have one more proton (and electron) than the one before it.
Atoms of elements in the some group in the Periodic Table
have the some number of electrons in their outer shell.
Atoms of elements in the some group in the Periodic Table
have the some number of electrons in their outer shell.
Patterns in the Periodic Table
alkali metals (from Group 1) so reactive
all atoms, they want to react to get a full outer shell.
when they react, they wont to lose that 1 electron
Group 1 elements ore so reactive
because it is easy for them to get rid of just 1 electron.
Metals get more reactive going down Group I
electron gets easier to remove as you go down the group.
electrons ore negatively charged.
They are attracted to the positive protons in the nucleus.
As you go down the group, the atoms get bigger.
Therefore the outer electron gets further away from
the attractive force of the nucleus.
This makes it easier for on electron to escape
from a bigger atom (even though the positive charge on the nucleus is greater).
The shielding effect
As well as distance from the
nucleus, another factor affects the
attraction of a nucleus for the
electrons in the outer shell. The
inner shells of electrons shield the
outer electrons from the pull of the
nucleus.
The halogens get less reactive going down Group
Charged particles
when the alkali metals react,
they lose the electron from their outer shell.
Halogens gain an electron.
Assessment
1.Periodic table are arranged in order of
a. Atomic mass b. Atomic number c. Ions
2. Atoms of elements in the some group in the Periodic Tobie
have the some number of --------------------in their outer shell.
a. Proton b. Neutron c. electron
3. When an atom loss or gain electron it become
a. ion b. compound c. molecule
4. The inner shells of electrons ----------------the outer electrons from the pull of the nucleus.
a. save b. shield c. react
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