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
