Topic 3 Test Flashcards
(24 cards)
What types of substances usually join together to form ionic compounds?
Metal and non metal
Describe ionic bonding
It is an electrostatic force of attraction between oppositely charged ions
What can be said about the strength of ionic bonds?
They are strong
Why do atoms gain or lose electrons?
They are more stable with a full outer shell of electrons i.e. the electron arrangement of a noble gas.
This is known as the Octet Rule of Thumb – when forming compounds atoms tend to have a stable electron arrangement like a noble gas with 8 electrons in the outer shell.
What always happens when metal atoms form ions?
e.g. write an equation to show how metal ions are formed from metal atoms, Na, Mg, Al
They lose electrons to form positive ions.
Na Na3+ + e-
Mg Mg2+ + 2e-
Al Al3+ + 3e-
How do you work out how many electrons a metal loses when it forms an ion?
Why do metal ions do this?
A metal loses electrons equal to the number of electrons in the outer shell.
They are more stable with a full outer shell of electrons.
What happens to non-metal atoms when they form ions?
i.e. write an equation to show how non-metal ions are formed from non-metal atoms, Cl, O, N
They always gain electrons to become negative ions.
Cl2 + 2e- 2Cl-
O2 + 4e- 2O2-
N2 + 6e- 2N3-
What type of substances have metallic bonding?
Metals
Metallic bonding is very strong
.
What type of elements usually form covalent compounds?
Non metals
What is a covalent bond?
A shared pair of electrons
Electrons hold covalent bonds together
.
For the 4 shape molecule and 5 shape molecule what are they’re names
Pyramidal for 4
Tetrahedral for 5
What type of bonding is found in a molecule
Covalent
Know that the molecules bonds are strong but the bonds between molecules are weak
.
What is a covalent network
A giant structure of covalent bonds
Name 2 compounds with a covalent network structure
Silicon carbide silicon dioxide
Why do covalent compounds not carry electricity
They have no charged particles to do so
Why do Ionic bonding conduct when as a liquid or molten state but not solid
The ions are free to move when molten or dissolved but they are not free to move when solid as they are held in a lattice structure.
Properties of ionic compounds
High melting and boiling points - Ionic bonds are very strong - a lot of energy is needed to break them. So ionic compounds have high melting and boiling points.
Conductive when liquid - Ions are charged particles, but ionic compounds can only conduct electricity if their ions are free to move. Ionic compounds do not conduct electricity when they are solid - only when dissolved in water or melted.
Eg sodium chloride
Properties of metallic compounds
Very strong melting point due to strong bonds which are hard to break.
Delocalised electrons which help carry current
Properties of covalent compounds
Poor conductors of electricity because no charges particles or delocalise electrons
and low melting and boiling due to weak bonds
Properties of magnesium
High melting and boiling point
Flammable as it burns in air
Network and lattice have high melt points
.
