Group 7 elements

1. Why Chlorine is
added in
swimming pool
• Chlorine is added to the
water to kill germs. When
it is added to a
swimming pool, it forms
a weak acid called
hypochlorous acid that
kills bacteria like
salmonella and E. coli, as
well as germs that cause
viruses such as diarrhea
and swimmer's ear.

2. Write the name of group 7 elements from the
periodic table
• The group 7 elements contains 5 elements and they are :
• Fluorine
• Chlorine
• Bromine
• Iodine
• Astatine

3. Group 7 elements are non – metals. Suggest
their physical properties
• They do not conduct electricity.
• They are poor conductors of heat.
• They have low melting and boiling point

5. Melting and Boiling Point
Element Melting point
(*C)
Boiling point
(*C)
State at 20 *C Colour
Fluorine -220 -188 Gas Yellow
Chlorine -101 -35 Gas Green
Bromine -7 59 Liquid Dark red
Iodine 114 184 Solid Solid-shiny grey-
black vapour-
purple

6. Valence electrons
• How many electrons does fluorine
and chlorine atom have?

7. Ionic bond
• A bond formed
between metal and non
metal by losing or
gaining an electron

8. Ionic bond –
metal halides
• When a metal join with
non metal it gains or
loses electron to form a
compound. Halogens
lose one electron and
form an ionic bond
with a metal to form
metal halides

9. Metal + halogens – salt
• Example
• Sodium + chlorine ------ sodium chloride
• Potassium + fluorine ----- Potassium fluoride
• Iron + bromine ------- Iron bromide

10. Task 1:Arrange the group 1 elements with their respective colours
symbols and state of matter
• Task 2:Compare group 7 elements with the property of group 1 elements
and group 2 elements
• Task 3:Draw the ionic bond formation between group 1 element with
fluorine and group 2 elements with fluorine. Write the name of the
compound. Predict the chemical formula if group 1 element or group 2
elements react with group 7 elements.

11. Group 7 element exist as diatomic
molecules or diatomic compounds.
•Guess why?????

12. Identify the below chemical formula as
compounds or molecules.
• CH4-
• H2-
• Cl2
• C6H12O6
• NH4
• F2
• Br2

13. Learning Objectives
• To understand what are diatomic molecules
• To explain why group 7 elements exist as diatomic molecules.
• To know about the intermolecular and intramolecular attraction between
group 7 elements

14. Why Group 7 elements exist as molecules?
• How many valence electron does group 7 elements have?
• How many electrons does group 7 element need to complete its octet
structure?
• If two group 7 elements combine together can they complete its octet
structure
• Group 7 elements are one of the diatomic molecules.

15. List of diatomic molecules
• Hydrogen (H2)
• Nitrogen (N2)
• Oxygen (O2)
• Fluorine (F2)
• Chlorine (Cl2)
• Iodine (I2)
• Bromine (Br2)

16. How to remember
easily?
• All Halogens exist as
diatomic molecules.

18. Task 1:Separate the given chemical formulas as
compounds or molecules
• Task 3:Draw the intra molecular and intermolecular attraction
between fluorine, hydrogen and oxygen.
• Task 2:Draw the bonding of fluorine with another fluorine atom.
Name other elements which also exist as diatomic molecules. Suggest
an easy way to remember them.

19. The Group 7 Elements

20. Guess what?
Fluorine bonds with fluorine
Fluorine bonds with Lithium
Fluorine bonds with hydrogen.
What is the difference between each bonding?

21. Learning Objectives
• To differentiate between ionic and covalent bonding of halogens
• To draw the bonding between fluorine and fluorine atom
• To write a chemical formula and write the name of the compound of ionic
and covalent bonding compounds of halogens

22. Ionic bond of
halogens with
group 1 element
• Sodium +
chlorine
• Sodium
chloride

23. Lithium + Fluorine----- Lithium Fluoride

24. Covalent
bonding
• Chlorine
molecule

25. Fluorine molecule

26. Task 1: Sort the given pieces of compounds as
ionic bond and covalent bond.
•Task 2: Draw any two ionic bond between
group 1 elements and halogens.
•Task 3: Draw a Venn diagram representing
the similarities and differences between Ionic
bond and covalent bond

27. Melting and Boiling Point
• The group 7 element have low melting and boiling points compared to most
metals. This is because they exist as molecules.
• A strong force holds the two atoms of the molecule together. The forces
between a molecules and its neighbours are weak. It is easy to separate the
molecules of chlorine in the liquid state to form a gas.
• The table in the previous page shows a trend in melting and boiling points.
They increase from top to bottom of the group. This is because the atoms
(and molecules) of the elements get bigger.

28. Covalent Bonding
of group 7
elements
• Group 7 elements
donot exist as single
atoms they are always
found as molecules or
compounds.
• Ex F2 or Cl2

29. Review
• Group 7 elements are also called as halogens
• It has relatively low melting and boiling point
• Group 7 elements are one of the diatomic molecules and have
intermolecular attraction between the atoms.
• They react with metals to form salt.
• Only group in periodic table which have different states is halogens with
different colours on burning

30. What do you mean by diatomic molecules?
Other than group 7 elements name some other
diatomic molecules
• Diatomic molecules consist of two atoms bonded together. In contrast,
monatomic elements consist of single atoms (e.g., Ar, He). Many compounds
are diatomic, such as HCl, NaCl, and KBr. Diatomic compounds consist of
two different elements. There are seven pure elements that form diatomic
molecules.