Covelent Bonding Flashcards
Why can’t non-metals bond together by transfer of electrons?
Non-metals cannot bond together by transfer of electrons, because too many electrons would need to be transferred.
What do non-metals do instead of transferring electrons?
Instead, non-metals achieve a full outer shell by sharing electrons.
I a covalent bond, what are the nuclei attracted to?
In a covalent bond, each of the nuclei is attracted to the shared pair of electrons.
What happens when a simple molecular substance is heated?
When the substance is heated it is the intermolecular forces that are overcome, not the covalent bond in each molecule. The intermolecular forces are weak so not much energy is needed to break bonds.
What is a molecule in a covalent structure?
A molecule is a particular produced by a small number of covalent atoms bonded together.
Do molecules conduct electricity?
Molecules don’t carry charge, so don’t conduct electricity.
What is the identity of an element determined by?
The relative atomic mass.
An element with one electron in its outer shell is a ….
Reactive metal.
Giant covalent structures - Diamond
A giant covalent structure with a very high melting point due to strong bonds between carbon atoms - 4 bonds per carbon.
Giant covalent structure - Graphite
Carbon atoms arranged in a layered structure, with free electrons in between each layer, enabling carbon to conduct electricity - 3 bonds per carbon.
Giant covalent structure - Silicone dioxide (sand)
A giant covalent structure of silicone and oxygen atoms with strong bonds causing a high melting point and it’s a good insulator as it has no free electrons - 4 bonds to oxygen atoms per silicone atom.
Why can graphite conduct electricity?
There is one delocalised electron that an move around with each atom because there is only 3 covalent bonds per carbon atom.
Why can graphite be used in pencils and as a lubricant?
The layers are easy to slide over each other as there is a weak force between the layers.
Metallic bonding…
There is strong attractive electrostatic forces between positively charged ions and a negatively charged ‘sea of electrons’ - electrons are not confined to any one atom.
Malleability + ductility:
The layers of ions are able to slide over each other.
Electron + heat conductivity:
Delocalised electrons can move through structure.
High melting points:
Strong metallic bond requires a lot of energy to break.
What is an alloy?
An alloy is a mixture of a metal and another element which has improved properties from the metal elements that make it.
How does the other element make the alloy stronger than the parent metal?
The other elements in the structure can change the properties of the alloy by preventing the metal ions from sliding over each other. This makes the alloy tougher and stronger than the parent metal.
What is stainless steel?
Steel with chromium and nickel.
When steel has a high carbon change the it is…
Strong but brittle.
Steel with low carbon content is…
Easily shaped.
