Topic 3: Structure And Bonding Flashcards
What are the properties of metals?
- Dense.
- Shiny.
- Ductile- stretch into wires.
- Good electric and thermal conductors.
- They are all have regular arrangements.
Why are metals malleable and ductile?
-This is because they are made of a large 3D lattice, the layers can slip over each other.
What kind of structure does metallic bonding have?
-Giant Structure.
Different structures?
- Face centered cubic E.g. Al.
- Hexagonal close packed e.g. Mg.
- Body centered cubic e.g. Na.
Define ionic bonding?
-Occurs between a metal and a non-metal- it is the complete transfer of one or more electrons metal to non-metal, giving charged ions that electrostatically attract.
Metals in groups 1,2,3?
-These can get full outer-shells most easily by losing all there outer electrons, to leave positive ions- this process is called oxidation.
Non-metals in groups 6-7?
-These can get to a full outer shell by accepting enough electrons from a metal to make hen up to a 8, forming negative ions- this process is called reduction.
Melting points of ionic compounds?
-This depends of the strength of the forces of attraction, this is therefore the melting point. The melting point increases as the charge increases. Eg Mg2+O2- has stronger forces of attraction then Na+Cl-.
What effects the charge density?
- The size of an ion effects the strength of its forces of attraction.
- Ten forces of attraction between two small ions will be greater then those between two large ions with the same charge.
Ionic bonding only occurs in?
-Giant structures.
Electrostatic forces ionic bonding?
-There are strong electrostatic forces between oppositely charged ions.
What are the properties of ionic sodium chloride NaCl?
- High melting point.
- Non-conductive in its solid state, but when dissolved in water it becomes conductive.
Properties of ionic Magnesium oxide MgO?
- Higher melting point then sodium chloride, because of more charge 2+ and 2- greater ionic bonds.
- It also stays non-conductive because it stays solid at higher temperature.
Giant ionic substances form a…
-Giant ionic lattice.
Ionic solid properties?
- High melting point.
- Don’t conduct when solid but they do when dissolved in solution.
How are ions formed?
- Ions are electrically charged particles formed when atoms lose or gain electrons.
- They have the same electronic structures as noble gasses.
- Metal atoms lose electrons and form positive ions.
- Non- metal gain electrons, atoms form negative ions.
- The strong electrostatic forces of attraction between oppositely charged ions are called ionic bonds.
- Ionic compounds have high melting and boiling points.
Examples of ionic bonds and ionic compounds?
- NaBr sodium bromide.
- KBr potassium bromide.
- NaCl sodium chloride.
- KI potassium iodide.
When do you get a covelent bond?
-When a non-metal and a non-metal need to bond.
What is a covalent bond?
-A bond with a shared pair of electrons. This is when two non-metals combine they both need to gain electrons, and they can do this by sharing two electrons in a covalent bond.
What is a simple molecular structure?
-This is a molecular structure that consists of small molecules, with weak forces of attraction (intermolecular forces between molecules).
Properties of Simple molecular?
- They have low boiling points, so not much energy is needed to break the forces of attraction, also low melting points.
- They do not conduct electricity at all as they have NO CHARGED PARTICLES.
- Often dissolve in non-polar solvents such as hexane
- Also insoluble in water.
Properties of Giant covalent structures?
- They have many bonds 3-4.
- A lot of non-metal atoms each joined with covelent bonds.
Giant covelent lattice structure?
-Normally a giant arranged into giant regular latices- these are extremely strong because of the many bonds.
What is a Allotropes?
-When elements exist in more then one form such as carbon and diamond.
Properties of giant covalent?
- They are hard.
- They have very high melting points.
- Insoluble in all solvents.
- They don t conduct electricity in solid or when molten, this is because of the lack of charged particles.
Example of giant covelent?
- Diamond- each atom is bonded to four neighbors, it is a crystal and very strong.
- Graphite - honeycomb structure that has layers with strong covelent bonds holding them together.
- It requires a lot of energy to break the strong covalent bonds.