Chemistry - Bonding, Structure & Properties of Matter Flashcards
What are ionic substances?
Substances made from ions (which are electrically charged particles that have a different number of protons and electrons).
What is the structure of ionic substances?
A giant lattice - where positive and negative ions are attracted to each other by electrostatic attractions (known as ionic bonding)
What are the melting and boiling points of ionic substances and why are they this way?
They are high - because the strong attraction between positive and negative ions has to be overcome, so this requires a lot of energy - e.g.: NaCl melts at 801 degrees.
Can ionic substances conduct electricity?
An electric current is the flow of electrically charged particles (e.g.: ions or electrons). Ionic substances are made of ions but they cannot move when they are in a solid so cannot conduct electricity.
But when melted, the ions can move so they can conduct electricity. Many can do this when they are dissolved in water.
How do you work out the charge of an ion?
- Look at what group they’re in on the periodic table
- Group 1 has 1 electron in its outer shell, it it must lose 1 to become an ion, therefore will be +1
What is the charge of an oxygen ion?
O2- … oxygen has 6 electrons in its outer shell, so gains 2 and becomes -2 charge.
How do you work out the formula of an ionic substance?
The number of positive charges must equal the number of negative charges.
E.g.: Magnesium chloride - Magnesium has 2+ charge, Chloride has 1- … so it must be MgCl2
What is the formula of Aluminium Oxide?
Aluminium is 3+
Oxygen is 2-
So must be Al2O3
How are ionic compounds form?
When metals react with non-metals. Electrons are transferred from the outer shell of the metal atom to the non-metal atom.
E.g.: Sodium with chlorine - each sodium ion loses one electron to the chlorine atom.
How do you draw a diagram of metals donating electrons to non-metals?
As a ‘dot and cross’ diagram
What are molecular substances?
Substances made of molecules - molecules are neutral particles made from atoms joined together by ‘covalent’ bonds.
What are ‘covalent bonds’?
When two atoms join together and share electrons.
E.g.: H2O
What is the structure of molecular substances?
Within each molecule there are strong covalent bonds … however when they come together there are weak forces between the molecules, called ‘intermolecular forces’.
What are the melting and boiling points of molecular substances and why are they this way?
They are low because the weak intermolecular forces between molecules are easy to overcome - e.g.: water boils at 100 degrees.
Why cant molecular substances conduct electricity?
Molecules are electrically neutral do they cannot conduct electricity
How do you draw molecular structures?
As a stick diagram or as a dot and cross diagram
Draw a dot and cross diagram of carbon dioxide
