What is the uses of iodine?

• A solution containing potassium iodide (KI) and iodine in alcohol is used to disinfect external wounds. Elemental iodine is also used as a disinfectant. 
• Silver iodide is used in photography. 
• Iodine is sometimes added to table salt to prevent thyroid disease. 
• Iodine’s other uses include catalysts, animal feeds and printing inks and dyes. 
• Iodine is used in many household cleaning products available from well-known supermarkets. 
• The health benefits of iodine include the formation of healthy and shiny skin, teeth, and hair. It is an important element for hair care, as lack of this mineral can result in hair loss. Moreover, it also speeds up hair growth and increases follicle strength. 
• Iodine influences the functioning of thyroid glands by assisting in the production of hormones, which are directly responsible for controlling the body’s base metabolic rate.  
• Iodine plays an important role in maintaining optimal energy levels of the body by ensuring the efficient utilization of calories, without allowing them to be deposited as excess fats. 
• A sufficient quantity of iodine in pregnant women is essential to prevent stillbirths or neurocognitive conditions like cretinism in the newborn babies.  

What is the uses of chlorine?

• Chlorine is used for producing safe drinking water and treat swimming pool water. Chlorine kills bacteria – it is a disinfectant.  
• It is also used to make hundreds of consumer products from paper to paints, and from textiles to insecticides. 
•  About 20% of chlorine produced is used to make PVC. This is a very versatile plastic used in window frames, car interiors, electrical wiring insulation, water pipes, blood bags and vinyl flooring. 
•  Another major use for chlorine is in organic chemistry. It is used as an oxidising agent and in substitution reactions.  
• Chlorine is also used for the manufacture of chlorates and it is important in organic chemistry, forming compounds such as chloroform, carbon tetrachloride, polyvinyl chloride, and synthetic rubber. 

What is the uses of fluorine?

• Fluorine is a highly reactive element that is used in processing nuclear fuel, in producing plastics and as a glass etching solution.   
• It can also be found in toothpaste and drinking water, which help prevent dental cavities and it is a component in air conditioning and refrigeration.  
• Because of its highly explosive nature, it is also used in rocket fuels. 
• Fluorine is used to refine uranium, which is used in nuclear reactors. 
• Fluorine is a component of chlorofluorocarbons. Chlorofluorocarbons were used as refrigerants in air conditioning units and freezers until they were banned because of their contribution to ozone depletion. 
• Fluorochemicals, including many high-temperature plastics such as Teflon, are also made using fluorine. 
• Hydrofluoric acid can dissolve glass and is used to etch the glass in light bulbs and in other products. 

What is the uses of bromine in our daily lives?

• Bromine is used in everyday products such as pesticides and water treatment solutions.  
• Bromine is a reddish-brown gas that has a pungent smell and can irritate the skin, nose and eyes. 
• Bromine compounds work as soil fumigants to prevent insects from attacking plants. Most pesticide agents contain bromine because it is toxic when inhaled.  
• Flame-retardant plastics often contain bromine. Brominated flame retardants are used in televisions, computers, domestic appliances, mobile phones, furniture, upholstery and mattresses. 
• Bromine is also used to purify water, as the agent acts as a disinfectant. Bromine is often used to treat swimming pools and hot tubs. Moreover, bromine compounds control algae and bacterial population growths. 
• Photography film is developed using bromine agents, which allow the photographs to develop sufficient light levels. 
• Several over-the-counter medications and prescription drugs contain bromine compounds. For example, most antihistamines, sedatives and analgesics contain bromine. Several drugs used to treat cocaine addiction and pneumonia contain active bromine ingredients. New studies show the effectiveness of bromine-containing drugs used to treat AIDS, Alzheimer's disease and cancer. 
• The car industry is beginning to use bromine compounds for electric car batteries. The batteries are designed to produce zero emissions. 

SPM Form 4: Periodic Table of elements (Checklist)

• Periodic Table: the table showing the elements in order of increasing proton number; similar elements are arranged in columns called groups.
• Group: A vertical column of elements in the Periodic table.
• Period: A horizontal row of the Periodic Table; its number tells you how many electron shells there are.
• Alkali metals: the Group I elements of the Periodic Table, which include lithium, sodium, potassium, rubidium, caesium and francium.
• Alkaline earth metals: the Group II elements of the Periodic Table, which include beryllium, magnesium, calcium, strontium, barium, and radium.
• Halogens: the Group VII elements of the Periodic Table, which include fluorine, chlorine, bromine, iodine and astatine.
• Noble gases: the Group 18 elements of the Periodic Table; they are called ‘noble’ or inert gases because they are so unreactive, which include helium, neon, argon, krypton, xenon and radon.
• Transition elements: the elements in the wide middle block of the Periodic Table (elements in group 3 to group 12).
• Metal: an element that shows metallic properties (for example conducts electricity, and forms positive ions)
• Non-metal - an element that does not show metallic properties: the non-metals lie to the right of the zig-zag line in the Periodic Table.
• Amphoteric oxide: An oxide that exhibits both acidic and basic properties.
• The atomic radius is a term used to describe the size of the atom.
• The ionization energy is the energy required to completely remove an electron from a gaseous atom or ion.
• Electron affinity reflects the ability of an atom to accept an electron. It is the energy change that occurs when an electron is added to a gaseous atom.
• Electronegativity is a measure of the attraction of an atom for the electrons in a chemical bond. The higher the electronegativity of an atom, the greater its attraction for bonding electrons.

Explain the reactivity of halogens decreases when going down Group 17.

The atomic size of halogen increases when going down Group 17. Thus, the outermost occupied shell becomes further away from the nucleus. Hence, the strength of the nucleus to pull another electron into the outermost occupied shell becomes weaker. Thus, halogens are less reactive when going down Group 17. 

Predict the physical and chemical properties of astatine

Predict the physical and chemical properties of astatine. Astatine is placed below iodine in Group 17 of the Periodic Table.

 

Physical properties of astatine:

• Black solid
• Has low melting and boiling points
• Has a low density
• Cannot conduct electricity
• Poor conductor of heat
• Slightly soluble in water

Chemical properties of astatine:

• Astatine reacts with cold sodium hydroxide solution to form sodium astatide, sodium astatate (I) and water.

At_{2 (s)} + 2NaOH _(aq) → NaAt _(aq) + NaOAt _(aq) + H₂O _(l)

• Astatine vapour reacts with heated iron wool to form a brown solid of iron wool to form a brown solid of iron (III) astatide.

2Fe _(s) + 3At_{2 (g)} → 2FeAt_{3 (s)}

Overview of Periodic Table

• Alkali Metals (Group 1) : All group 1 metals have one valence electron. When they form ions, they will have a charge of 1+. Group 1 alkali metals are highly reactive and will react vigorously with water.

• Alkali Earth Metals (Group 2): All group 2 metals have two valence electrons. When they form ions, they will have a charge of 2+. Group 2 alkaline earth metals are highly reactive and will react with water.

• Transition Metals (Groups 3–10, d block): Transition metals are famous for the colored salts and colored solutions they form. Many gems contain numerous transition metals. It is hard to predict the charge of a transition metal ion because the transition metals have multiple oxidation states. One transition metal, Hg, exists as a liquid at room temperature.

• Halogens (Group 17): Halogens (salt formers) have seven valence electrons and form ions with a charge of 1−. The halogens exist in three phases at room temperature. Fluorine is a pale-yellow gas, chlorine is a green gas, bromine is a brown-orange liquid, and iodine is a purple solid.

• Noble (Inert) Gases (Group 18): Noble gases have a full outer shell and will not react to form ions or share electrons.

• Lanthanides and Actinides (f Block): These elements have their valence electrons located in the f orbitals and are radioactive in nature.

Halogens on the Periodic Table

The halogens are located in Group VIIA of the periodic table, and are a particular class of nonmetals. The halogen elements are fluorine, chlorine, bromine, iodine, astatine.  These reactive non-metals have seven valence electrons. Halogens range from solid (I₂) to liquid (Br₂) to gaseous (F₂ and Cl₂) at room temperature. The chemical properties are more uniform. The halogens have very high electronegativities. Fluorine has the highest electronegativity of all elements. The halogens are particularly reactive with the alkali metals and alkaline earths, forming stable ionic crystals.

Summary of Common Properties

·         Very high electronegativities

·         Seven valence electrons (one short of a stable octet)

·         Highly reactive, especially with alkali metals and alkaline earths