Topic 2 – Bonding, Structure, and The Properties of Matter Flashcards
(39 cards)
What is a metallic bond?
A metallic bond is the electrostatic force of attraction between delocalised outer shell electrons and metal ions.
Structure of metals
Giant metallic lattice
Why do metals have high melting points and boiling points?
Giant lattice structure of many strong metallic bonds require lots of heat energy to break
Why are metals malleable and ductile?
Metal’s layers of ions can slide over each other, but are still held together by the delocalised electrons
Why are metals good conductors of thermal and electrical energy?
Delocalised outer shell electrons allow heat to flow through the whole structure.
What is an alloy?
An alloy is a mixture of a metal element and other elements
Why are metal alloys harder than pure metals?
The layers have been distorted and cannot slide over each other
Which elements make bronze?
Copper, tin
Which elements make brass?
Copper, zinc
Which elements make soldier wire?
Lead, sulfur
Which elements make duralumin?
Aluminium, copper
Which elements make stainless steel?
Iron, carbon, chromium & other elements
What is ionic bonding?
lonic bonding is the electrostatic attraction between positive and negative ions. It is a relatively strong attraction.
How are ionic compounds held together?
• They are held together in a giant lattice.
• It’s a regular structure that extends in all directions in a substance.
• Electrostatic attraction between positive and negative ions holds the structure together.
State properties of ionic substances
• High melting and boiling point (strong electrostatic forces between oppositely charged ions)
• Do not conduct electricity when solid (ions in fixed positions).
• Conduct when molten or dissolved in water - ions are free to move.
Give 5 examples of positive ions and 5 examples of negative ions (give names of negative anions).
E.g. Positive: Na, Mg?+, Al3+, Ca?+, Rb
E.g. Negative: CI, Br, SO 2-, NO; ; OH- (chloride, bromide, sulfate, nitrate, hydroxide).
What is important when working out a formula of an ionic compound?
lonic compounds are electrically neutral, i.e. positive and negative charges balance each other.
How are ionic compounds formed? Explain in terms of MgO case.
Reaction of a metal with a non-metal. Electron transfer occurs - metal gives away its outer shell electrons to non-metal. Mg is in Group II, so has 2 available outer shell electrons. O is in Group VI, so can accept 2 electrons to get a full outer shell configuration.
Mg becomes Mg?+ and O becomes 0?- (oxide).
What is a covalent bond?
Covalent bond is a shaired pair of electrons between two atoms.
Describe the structure and properties of simple molecular covalent substances
- Do not conduct electricity (no ions)
- Small molecules
- Weak intermolecular forces, therefore:
- Low melting and boiling points
How do intermolecular forces change as the mass/size of the molecule increases?
They increase. That causes melting/boiling points to increase as well (more energy needed to overcome these forces).
What are polymers?
Polymers are very large molecules (>100s, 1000s of atoms) with atoms linked by covalent bonds.
What are thermosoftening polymers?
Thermosoftening polymers - special type of polymers; they melt/soften when heated. There are no bonds between polymer chains. Strong intermolecular forces ensure that the structure is solid at room temperature. These forces are overcome with heating - polymer melts.
What are giant covalent substances? Give examples
- Solids, atoms covalently bonded together in a giant lattice.
- High melting/boiling points - strong covalent bonds.
- Mostly don’t conduct electricity (no delocalised electrons)
- Diamond, graphite, silicon dioxide.
