bonding, structure and properties of matter Flashcards
what is ionic bonding?
form between metals and non-metals. It involves the transfer of electrons in the outer shells.
what is covalent bonding?
When atoms share pairs of electrons, they form covalent bonds. These are STRONG bonds
Examples of covalently bonded substances with giant covalent structures:
diamond and silicon dioxide.
What are the three types of structure that can be formed by
covalent bonding?
Small molecules, very large molecules, giant covalent molecules.
What are the limitations of using dot and cross diagrams to
represent covalent bonds?
It shows the electrons differently, when they are the same and it does not show the bond angles or shape of the molecule.
The electrons in the outer shell of metal atoms are delocalised and are free to move throughout the structure.
The sharing of delocalised electrons lead to ….
strong metallic bonds.
How are atoms arranged in a metal?
Giant structures of atoms, arranged in a regular pattern,
delocalised electrons.
Why are metallic bonds so strong?
Sharing of delocalised electrons.
What are delocalised electrons?
They are free-moving electrons within structure; not associated with a particular atom.
Why are the particles that make up a metal described as positively charged?
The metal atoms lose outer shell electrons and therefore there are more protons (+) than electrons (−).
solids (s) =
Close together, regular pattern, vibrate on the spot.
liquids (l) =
Close together, random arrangement, move around each other.
gases (g) =
Far apart, random arrangement, move quickly.
aqueous solution (aq) =
water that contains one or more dissolved substance.
solid → liquid =
melting
liquid → gas =
evaporation
gas → liquid =
condensation
liquid → solid =
freezing
gas → solid =
deposition
solid → gas =
sublimation
Melting and freezing take place at ….
the melting point
Boiling and condensing take place at ….
the boiling point
The stronger the forces between the particles the ….
higher the melting and boiling point of the substance.
What factor affects the amount of energy needed to change
state?
Forces between molecules.
Describe the structure of ionic compound
Regular, giant ionic lattice
Why do ionic compounds have high melting and boiling points?
Strong electrostatic forces of attraction between ions.
Why can ionic compounds conduct electricity when melted or dissolved in water?
Ions are free to move, carry the charge.
Why do small molecules have low melting and boiling points?
Weak forces between molecules/ intermolecular forces.
What happens to the melting and boiling points as small
molecules get bigger? Why?
Increases, intermolecular forces get bigger.
What are polymers?
Very large molecules made of repeating units.
Why are polymers normally solid at room temperature?
Intermolecular forces relatively strong.
What is an alloy?
Mixture of two elements, one of which is a metal.
Why are metals good conductors of electricity?
Electrical charge carried by delocalised electrons.
In a diamond, how many covalent bonds does each carbon make?
4
Diamond does not conduct electricity. Why?
No delocalised electrons.
In graphite, how many covalent bonds does each carbon make?
3
Why is graphite soft?
Layers can slide over each other, weak forces between layers, no covalent bonds between layers.
How is graphite similar to metals?
It contains delocalised electrons.
