C2.4 Flashcards
What is a chemical bond
A bond that holds atoms together
How are these bonds formed
Ionic
Simple molecular covalent
Giant molecular covalent
Metal ion loses electron to become positive and non metal gains it and becomes negative ion
Strength of bonds
Ionic are strong
SCM are strong in molecules but weak forces hold separate molecules together
GCM are strong with the bonds found between all the atoms in the structure
Melting and boiling points of bonds
Ionic high because lots of energy needed to break bonds
SCM low so gases or liquids at room temp
GCM high as lots of energy needed to break covalent bonds
Solubility of bonds
Ionic are often soluble
SCM some are soluble
GCM are insoluble
Conductivity
Ionic only conduct when in aqueous solution or molten so charged ions can move freely
SCM don’t conduct
GCM don’t conduct unless graphite as it has one free electron per carbon atom
Properties of metals
Malléable High melting point apart from mercury Conductive Shiny Hard
What are delocalised electrons
Electrons not fixed to a specific atom such as in metals where they are free to move in a sea of electrons
What happens when potential difference is applied to a metal
The freely moving electrons then begin to travel in the same direction and create a currant
Why are metals malleable
The sea of electrons help hold the atoms together so when hit, instead of breaking, the atoms move and spread out
What are alkali metals and properties
They are the metals in group one and are metals. They have low melting points for metals and all can be cut with a knife. They are very reactive as they lose their outer electron easily. Reactivity increases the lower in the table you go
Alkali metal and water reaction
Alkali metal + water —> metal hydroxide + hydrogen
Why does reactivity increase with the more Shells
To react, the alkali metal must lose its outer electron. The forces of attraction between the protons in the nucleus and electrons in the shell is stronger the closer the electron is to the nucleus. The more shells there are, the further the outer electron is so the weaker the force between it and the nucleus so the easier it reacts
What are halogens and properties
Elements in group 7, they are gases at the top and become liquids and solids the lower in the table they are. They are quite reactive and are more reactive the closer they are to the top
Metal plus halogen reaction
Metal + halogen —> metal halide
Why does reactivity decrease the lower in the table for halogens
To react, it must gain an electron in the outer shell. It’s easier to gain an electron in a shell nearer the nucleus as forces of attraction between electron and proton are greater so the closer the outer shell, the more reactive it is. The opposite for alkali metals
What is a displacement reaction
When a more reactive metal becomes in contact with another compound and displaces the metal from its compound and takes its place e.g.
Iron + copper sulphate —> copper + iron sulphate
Halogen and hydrogen reaction
Hydrogen + halogen —> hydrogen halide
Hydrogen halide + water —> acid
What are noble gases
Gases in group 8/0 that are very un reactive as they have full outer shells. They are intert
Uses of argon
Used to be used in filament lamps to stop hot filament reacting with oxygen in the air and burning.
Used in welding to form a hot blanket over the metal so that it doesn’t react with oxygen in the air
Used in fire extinguishing as it’s not flammable and will suffocate the fire depriving it from oxygen
Uses of xenon
Used to be used in lights like argon
Uses of helium
Very low density so good for balloons and air ships as it will float
Uses of neon
Used in fluorescent lamps as produces a red light when currant is passed through it at low pressure
