Bonding,Structure and Properties of Matter

What is ionic bonding?

• the electrostatic attraction between positive and negative ions, which is a relatively strong attraction

How are ionic compounds held together?

• held together in a giant ionic lattice

• regular structure that extends in all directions in a substance

What are the properties of ionic substances?

• high melting and boiling points (strong electrostatic forces between oppositely charged ions)

• do not conduct electricity when solid

• conduct when molten or dissolved in water

How are ionic compounds formed?

• reactions of a metal with a non-metal

• electron transfer, metal gives away its outer shell electrons to non metal

• metals become positive ions

• non metals become negative ions

• opposite charges attract each other

What is a covalent bond?

• a shared pair of electrons between two atoms

What is 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

What is metallic bonding?

• the electrostatic attraction between the positive metal ions and the negative delocalised electrons

How does metallic bonding occur?

• electrons in the outer shell of the metal atoms are delocalised so they are free to move around.

• there are strong electrostatic bonds between the positive metal ions and the shared negative electrons

Why are most metals solid at room temp?

• the electrostatic forced between the metal ions and delocalised sea of electrons are very strong, so need lots of energy to be broken

• meaning they have very high melting and boiling points

Why are metals good conductors of heat and electricity?

• the delocalised electrons carry electric charge and thermal heat energy through the whole structure, so metals are good conductors of electricity and heat

Why are most metals malleable?

• the layers of atoms in a metal can slide over each other

Why are alloys harder than pure metals?

• different elements have differently sized atoms, so when an element is mixed with a pure metal, new atoms will distort the layers of metal atoms making it more difficult for them to slide over each other.

Why are alloys sometimes used instead of pure metals?

• they are often too soft

• alloys are harder and therefore more useful

What element are diamond and graphite made up of?

• carbon

State the properties and structure of diamond

• each carbon atom is covalently bonded to 4 others

• hard - many strong covalent bonds in the structure

• high melting point - bonds require lots of energy to overcome

• poor electrical conductivity - no delocalised electrons to move and carry charge

state the properties and structure of graphite

• each carbon atom is covalently bonded to 3 others

• soft - weak forces between layers so they can slide over each other

• good electrical conductivity - each atom has a delocalised electron that can move and carry charge through the structure