Topic 6 - Groups in the Periodic table Flashcards
Give properties of metals. (5)
- Strong and hard
- High densities
- Malleable because layers of atoms in a pure metal can slide over each other.
- High melting points
- Good conductors of heat and electricity because the delocalised electrons in metals can carry an electrical current through the materials.
What is a metallic bond?
This is a bond between metals. Free electrons (negative) move around positive ions. Strong electrostatic force between positive metal ions + negative electrons.
Give examples of metallic bonding
Copper, Lead, Iron, Titanium
What is group 1?
Alkali Metals
Describe the reactivity of alkali metals.
- Needs to lose one electron to get a full outer shell,
- Reactivity increases as you go down group 1 as the distance between the nucleus and the outer electron increases making the force weaker. The outer electrons is more easily lost as it further from the nucleus - so it’s less strongly attracted to the nucleus and less energy is needed to remove it; essentially it is willing to react with more things to get a full outer shell.
Describe the reaction of lithium with water.
When lithium is added to water, lithium floats. It fizzes steadily and becomes smaller, until it eventually disappears.
What is the symbol equation of the reaction of lithium with water?
2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g)
Describe the reaction of sodium with water.
When sodium is added to water, the sodium melts to form a ball that moves around on the surface. It fizzes rapidly, and the hydrogen produced may burn with an orange flame before the sodium disappears.
What is the symbol equation of the reaction of sodium with water?
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
Describe the reaction of potassium with water.
When potassium is added to water, the metal melts and floats. It moves around very quickly on the surface of the water. The hydrogen ignites instantly. The metal is also set on fire, with sparks and a lilac flame. There is sometimes a small explosion at the end of the reaction.
What is the symbol equation of the reaction of potassium with water?
2K(s) + 2H2O(l) → 2KOH(aq) + H2(g)
What are the physical properties of alkali metals? (2)
- Low melting points and boiling points when compared with other metals
- Very soft - can be cut with a knife
What is group 0?
Noble gases
Describe the reactivity of noble gases
They are inert (nonreactive) because they have full outer shells.
What increases as you go down group 0?
Boiling point, melting point and density
Describe uses of noble gases (5)
Helium - Party balloons, airships - low density than air, helps to float
Neon - Red neon signs, lasers.
Argon - Shielding gas in arc welding - creates inert atmosphere to stop oxygen from reacting with the hot metal
Xenon - Lights, lasers.
Krypton - Lights, Photographic flashguns - stops the flash filament from from burning up during high temperature flashes
What is group 7?
Halogens
What are the colours and physical states of chlorine, bromine and iodine?
Chlorine (Cl2) is a fairly reactive poisonous, green gas
Bromine (Br2) is a poisonous, red-brown liquid which gives off a orange vapour at room temperature
Iodine (I2) is a dark grey crystalline solid which gives off a purple vapour when heated
What do halogens exist as?
They exist as diatomic molecules (Cl2, Br2, I2, etc). They share one pair of electrons in a covalent bond to give both atoms a full outer shell.
Describe the reactivity of group 7
A halogen atom only has to gain one electron to form a stable electronic structure. The easier it is for a halogen atom to attract an electron, the more reactive the halogen will be. As you go down group 6, it gets more reactive because it gets harder to attract the extra electron to fill the outer shell when it’s further away from the nucleus.
How can you use trends in physical properties of halogens to predict the properties of halogens further down the group?
You can use the trends in physical propeties from chlorine to iodine to predict the properties of halogens further down the group. For example, you can see that melting point increases down the group, and the colours of the halogens get darker so you could predict that astatine (which comes below iodine) would be a dark-coloured solid at room temperature and it is astatine is a black solid with a melting point of around 300 °C.
Describe the test for chlorine
You can test to see if a gas is is chlorine by holding a piece of damp litmus paper over it. Chlorine will bleach the litmus paper, turning it white. However, it may turn red at first as a solution is slightly acidic.
How are metal halides formed?
Halogen + metal ——> salt (metal halide)
How are hydrogen halides formed?
Halogen + Hydrogen ——> hydrogen halide
They can dissolve in water to form acidic solution
hydrogen + chlorine ——> Hydrogen chloride
hydrogen chloride + water ——> Hydrochloric acid
