Bonding Structure And Properties of Matter Flashcards
What are Allotropes
Allotropes are different structural forms of the same element in the same physical state
Diamond:
Strong covalent bonds - high boiling/melting points
It doesn’t conduct electricity - no free electrons
Giant covalent structure - makes diamonds hard
Graphite
Covalent bonds in the layers need loads of energy to break - high melting point
Each carbon atom has a delocalised electron - conducts electricity and thermal energy
No covalent bonds between the layers (free to move around) - makes it soft and slippery
How is hydroxide made?
Alkali + water = hydroxide
Properties of ionic compounds
High melting/boiling point
Can dissolve easily
When solid can’t conduct electricity
When NOT solid ions are free to move carrying current
Lattice structure with strong electrostatic attractions
What causes ions to form a ionic bond?
The electrostatic attraction between the oppositely charged ions causes them to come together to form a bond
Ionic Compounds only consist of…
Metals and non metals
Describe how sodium and chlorine react to form sodium chloride
When they react together the metal (Na) atom loses the electrons to form a positively charged ion and the non metals gains these electrons to form a negatively charged ion. These oppositely charged ions are strongly attracted to one another by electrostatic forces.
Models of covalent bonds
DOT AND CROSS - useful for showing which atoms the electrons in a covalent bond come from, but they don’t show the relative sizes of the atoms or how the atoms are arranged in space.
LINE - great for showing how atoms are connected in large molecules. However they don’t show which atoms the electrons in the covalent bond comes from
Covalent bonds happen in compounds of…
Non metals
Fullerenes
( molecules of carbon shaped like hallow balls)
Can be used to cage other molecules - can be used to deliver drugs into the body
A huge surface area - help make great industrial catalyst
They can form nanotubes:
can conduct electricity and thermal heat
High tensile strength ( don’t break when stretched)
Used in electronics or to strength materials ( tennis racket)
Alloys
They are harder than pure metal
Pure metal + other metals = alloys
An alloy is a mixture of two or more metals / a metal and other element (eg carbon)
Different elements:
Different sizes
When mixed with pure metal it distorts the layers of the metal atom
making it hard to slide against each other ( makes alloy harder than
pure metals)
Most metals are malleable
Layers of atoms in a metal can slide over each other making it malleable ( can be bent or hammered or rolled)
What does electrostatic attraction do?
They hold the atoms together in a regular structure and are known as metallic bonding - very strong
Simple molecular substances
Very strong covalent bonds
Forces between these molecule are very weak that why some of them are gas or liquid at room temperature.
Melting/boiling point is low because the molecules are easily parted from each other.
