Bonding, Structure And The Properties Of Matter Flashcards
What is ionic bonding?
Ionic bonding is bonds that have electrostatic attraction. When oppositely charged ions form an ionic bond you get an ionic compound.
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 and the electrostatic attraction between positive and negative ions holds the structure together.
State the 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 five examples of positive ions
Na+, Mg2+, Al3+, Ca2+, Rb+
Give five examples of negative ions
Cl-, Br-, O2-, S2-, I-
What is important when working out a formula of an ionic compound?
Ionic compounds are electrically neutral, i.e. positive and negative charges balance each other.
How are ionic compounds formed?
Atoms gain or lose electrons, by transferring as both metal and non metal have an incomplete outer shell
What is a covalent bond?
A chemical bond formed when two or atoms share electrons.
Describe the structure and properties of simple molecular covalent substances
- Do not conduct electricity (no ions)
- Small molecules
- Weak intermolecular forces
- 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?
very large molecules with atoms linked by covalent bonds
What are thermosoftening polymers?
- soften when heated and shaped when hot
- harden when cooled, but can be reshaped when heated again
- EXAMPLE: polyethene
- slide past each other making it flexible
- forces between polymer chains are weak
What are giant covalent structures?
Giant covalent structures have huge networks of covalently bonded atoms. Carbon often forms this type of structure because they can each form four strong covalent bonds.
What are the properties of giant covalent substances?
- solids, atoms covalently bonded together in a giant lattice
- high melting/boiling points - strong covalent bonds
- mostly don’t conduct electricity
Describe and explain the properties of allotropes of carbon?
Diamond
- four, strong covalent bonds for each carbon atom
- very hard (Strong bonds)
- very high melting point (strong bonds)
- does not conduct (no delocalised electrons)
Graphite
- three covalent bonds for each carbon atom
- layers of hexagonal rings
- high melting point
- layers free to slide as weak intermolecular forces
between layers; soft, can be used as a lubricant
- conduct thermal and electricity due to one delocalised
electron per each carbon atom
Fullerenes
- hollow shaped molecules
- based on hexagonal rings but may have
5/7-carbon rings
- C60 has spherical shape, simple
molecular structure (Buckminsterfullerene)
Nanotubes
- cylindrical fullerene with high length to
diameter ratio
- High tensile strength (strong bonds)
- Conductivity (deloc. electrons)
Graphene - a single layer of graphite.
What is metallic bonding?
Forces of attraction between delocalised electrons and nuclei of metal ions.
Describe the properties of metals
- High melting/boiling points (strong forces of attraction)
- Good conductors of heat and electricity (delocalised electrons)
- Malleable, soft (layers of atoms can slide over each other whilst maintaining
the attraction forces)
What are alloys? Why are they harder than pure metals?
Alloys:
- mixtures of metal with other elements, usually metals
- different sizes of atoms distorts the layers, so they can’t slide over each other,
therefore alloys are harder than pure metals
What does the amount of energy needed to change state from solid to liquid or liquid to gas depend on?
The strength of the forces between the particles of the substance. The nature of the particles involved depends on the type of bonding and the structure of the substance. The stronger the forces between the particles the higher the melting point and boiling point of the substance
What is a pure substance?
a substance in which there is only one type of particle
What temperature does a pure substance melt/boil at?
Fixed temperature
What temperature does a mixture melt/boil at?
Over a range of temperature
What are the three states of matter?
solid, liquid, gas
What is nanoscience?
Science that studies particles that are 1 - 100nm in size
