Group 7

• Group 7 is called the halogens.
• All the elements in group 7 are non-metals.
• Group 7 elements have 7 electrons in there outer shells.
• If we take two atoms of a group 7 element, they react with each other. Two atoms overlap their outer shells and they share a pair of electrons. This shared pair of electrons are a covalent bond.

  
• Every group 7 element form a molecule consisting of two atoms joined by a covalent bond.
• We can represent the covalent bond as a stick between the two atoms.
• We can use the melting and boiling points to work out the physical state of each halogen.
• Room temperature is around 20 degrees
• The melting and boiling points increase as we move down group 7.
• Fluorine and chorine are both gases at toom temperatures.
• Bromine is a liquid at room temperature. This is because the melting point of bromine is lower than 20 degrees but the boiling point is higher than 20 degrees.
• Iodine is a solid at room temperature, this because the melting point and boiling point are higher than 20 degrees.
• Relative molecular mass gives us an idea of the size of a molecule.
• As we move down the halogens, the relative molecular mass increases. In other words, the molecules get bigger moving down group 7.
• Group 7 elements form covalent compounds when they react with other non-metal elements.
• The compound formed between the halogen bromine and the non-metal carbon is a covalent compound.

  
• When halogens react with metals, they form ionic compounds.
• Halogens get less reactive as we move down group 7.
• Chlorine is less reactive that fluorine, this is because chlorine gains an electron less easily than fluorine. In a chlorine atom, there is a greater distance between the outermost electron and the nucleus. This means that the outer electrons are less attracted to the positive nucleus in a chlorine atom compared to a fluorine atom.
• A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt.
• When we look at the reaction between the compound sodium bromide and fluorine. The sodium bromide is an aqueous solution. This means that we've dissolved the sodium bromide in water.
• Fluorine is higher than bromine in group 7, this tells us that fluorine is more reactive than bromine. This means that the fluorine can push our or displace the bromine. This is a displacement reaction.