C2.4 Groups in the periodic table Flashcards
What affects the properties of a material?
The type of chemical bonding it has
What are covalent bonds?
Atoms that share electrons to get a full other shell, covalent bonds hold atoms together in molecules
What two types of bonds have high melting and boiling points?
Ionic and giant molecular covalent
What type of bond has low melting and boiling points?
Simple molecular covalent
What is the solubility of ionic, simple covalent and giant covalent bonds?
Ionic- many dissolve in water
Simple molecular covalent- some dissolve in water
Giant molecular covalent-insoluble in water
When do ionic bonds form?
When a metal reacts with a non-metal
When do covalent bonds form?
Between atoms of non-metal elements
What are the atoms in metals held together by?
Metallic bonds
What are some properties of metals?
- good conductors of heat and electricity
- don’t dissolve in water
- malleable
What are delocalised electrons?
Electrons that are not located at specific atoms
In what way do the delocalised electrons move between the positive ions?
Randomly in all directions
What happens to the electrons if a potential difference is applied to the metal?
The electrons start to drift off in one direction
What is the movement of electrons in one direction in an element called?
An electric current
Why are metals malleable?
The positive ions in a metal can slide over each other, and since they are still held together by sea of electrons the metal spreads out instead of breaking
What are two properties of transition metals?
They have high melting points and form coloured compounds
Where are most metals found in the periodic table?
In the central block where the transition metals are found
Where are the alkali metals found in the periodic table?
Group 1
What are two properties of alkali metals?
- solid at room temperature but have a low melting point in comparison to other metals
- they are all soft metals that can be cut with a knife
What forms as a result of an alkali metal reacting with water?
A metal hydroxide and hydrogen gas
Are metal hydroxides acidic or alkaline?
Alkaline
Why are the reactions of all alkali metals similar?
They all form ions with a charge of +1
What happens to the reactivity of alkaline metals as you go down the group?
It increases
Why does reactivity increase as you go down a group?
The further you go down a group the more electron shells they have. The further the electron shells are from the nucleus, the smaller the force between the positive charge of the nucleus and negative charges of the electrons, which means they are more likely to lose or gain an electron to gain a full outer shell
Where are the halogens found?
Group 7
What are two properties of halogens?
- they are all coloured elements
- they are all corrosive and toxic
What is produced from a reaction between a metal and a halogen?
A metal halide
Why do halogens all form ions with a charge of -1?
They are all missing an electron to complete their outer shell so they gain an electron and become negative
What is the most reactive halogen?
Fluorine
What is the least reactive halogen?
Iodine
What is a displacement reaction?
When a more reactive metal displaces a less reactive one from a compound
What happens when you dissolve a hydrogen halide in water?
It becomes an acid
What happens to a solution of sodium bromide when chlorine is added?
Chloride displaces the bromine salt and the solution turns from colourless to clear
What happens to a solution of potassium iodide when chlorine is added?
Chlorine displaces the iodide and the solution turns brown-black
Where are the noble gases found?
Group 0
What does it mean when an element is inert?
It is very hard to make them react
Why are group 0 elements inert?
They have full outer shells
How do elements in other groups gain full electron shells?
By forming ions or covalent bonds
Why are noble gases useful?
Because they are unreactive
What are some uses of noble gases?
- xenon and argon used to be used in filament lamps the stop the hot filament from reacting with oxygen and burning away
- argon and helium are used in welding, to form a blanket over the hot metal to stop it reacting with oxygen in the air
- argon is used in fire-extinguishing systems because it is non-flammable
- helium is used for filling up balloons and airships because of its low density
- neon is used in fluorescent lamps and advertising displays as it produces a red coloured light when an electric current is passed through the tube at low pressure
