Groups in the Periodic Table (2)
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What are the alkali metals?
all the elements in group 1 of the periodic table
What are some key properties of all alkali metals? • colour? • storage? • handling? • reactivity? • melting and boiling points? • softness/hardness? • bonding?
• silvery solids • have to be stored in oil • have to be handled with forceps (they can cause chemical burns on the skin) • very reactive • have low melting and boiling points • very soft • only form ionic bonds
What is the relationship between periods in the periodic table and reactivity? (specifically for group 1) and why?
the lower down the column you go, the more easily the outer electron is lost because it is further from the nucleus (so the atomic radius is longer) and it’s less strongly attracted to the nucleus, so less energy is needed to remove it
What is the general equation for the reaction of an alkali metal with water?
alkali metal + water -> metal hydroxide + hydrogen
What are the visible observations of reacting lithium with water? (period 1)
it will move around the surface of the liquid, fizzing furiously
What are the visible observations of reacting sodium with water? (period 2)
it will move around the surface of the liquid, fizzing furiously it will also melt in the heat of the reaction
What are the visible observations of reacting potassium with water? (period 3)
it will move around the surface of the liquid, fizzing furiously it will also melt in the heat of the reaction it will get hot enough to ignite the hydrogen gas being produced
What are the halogens?
the elements in group 7 of the periodic table
What is a similarity of halogens?
they exist as diatomic molecules
What are some trends of halogens? (3)
As you go down the column: - their melting and boiling points increase - their colours get darker - they get less reactive
What is chlorine at room temperature? (period 2)
a fairly reactive, poisonous, green gas
What is bromine at room temperature? (period 3)
a poisonous, red-brown liquid which gives off an orange vapour
What is iodine at room temperature? (period 4)
a poisonous, dark grey crystalline solid which gives off a purple vapour when heated
Describe a test for chlorine gas. (3 steps)
• Collect the gas in a test tube. • Put a strip of damp blue litmus paper into the tube. • If chlorine is present, the litmus paper will bleach and turn white. It may turn red for a moment (because the chlorine is acidic).
Why do halogens get less reactive as you go down the column?
it is harder for the halogen to attract an electron (and form an ion) when the atomic radius gets larger because the outer shell is further away from the nucleus
What happens when you react a halogen with a metal?
they will react vigorously to form salts called ‘metal halides’
What happens when you react a halogen with hydrogen?
hydrogen halides are formed
What are some properties of hydrogen halides? • solubility? • acidity?
• soluble • dissolve in water to form acidic solutions
How can you use displacement reactions to show the reactivity trend of halogens? (4 steps)
• Measure out a small amount of halide salt solution in a test tube. • Add a few drops of a halogen solution to it and shake the tube gently. • If you see a colour change, then a reaction has happened - the halogen has displaced the halide ions from the salt. If no reaction happens, there won’t be a colour change - the halogen is less reactive than the halide so can’t displace it. • Repeat the process using different combinations of halide salt and halogen.
What are the noble gases?
the elements in group 0
What are some key properties of noble gases? (4 things)
• inert (don’t react much at all) • non-flammable • colourless monatomic gases (at room temperature) • very low densities
What are the trends in physical properties of noble gases? (2)
as you go down the column: - density increases - melting and boiling points increases