Topic 2 Structure and bonding - Ionic bonding(School curriculum) Topic 1 in CPG and PMT Flashcards
Ions, ionic bonding, properties of ionic compounds
What is an ionic bond?
A bond between a metal and non-metal involving the transfer of electrons.
In terms of electrons, describe what happens to the metal and non-metal when an ionic bond forms
The metal atom loses electrons to become a positively charged ion (cation)
The non metal gains electrons to become a negatively charge ion (anion).
What is an ion?
An ion is an atom or group of atoms with a positive or negative charge.
If an ion is positively charged, has it lost or gained electrons?
It has lost electrons. There are fewer negatively charged electrons to cancel out the charge of the positive protons. This means the overall charge becomes positive.
Na+ (+ should be up high) has the atomic number 11 and the mass number 23. How many protons, neutrons and electrons are in this ion?
Protons: 11
Electrons: 10
Neutrons: 12
O2- (2- should be up high and smaller) has the atomic number 8 and the mass number is 16. How many protons, neutrons and electrons are in this ion?
Protons: 8
Electrons: 10
Neutrons: 8
Why do elements in groups 1, 2, 6 and 7 readily form ions?
So they become more stable and achieve the electron structure of the noble gases (group 8).
What type of ions do elements in group 1 and 2 form?
Cations (positive)
- Group 1 metals will form 1+ ions
- Group 2 metals will form 2+ ions
What type of ions do elements in groups 6 and 7 form?
They are non-metals so form anions (negative)
- Group 6 will form 2- ions
- Group 7 will form 1- ions
What does it mean if an ionic compound ends in -ide?
The compound contains 2 elements
What does it mean if an ionic compound ends in -ate?
The compound contains at least 3 elements, one of which is oxygen.
Describe the structure of an ionic compound
Lattice structure.
Regular arrangement of ions.
Ions held together by strong electrostatic forces between ions with opposite charges.
What is the chemical formula of sodium oxide, formed from Na+ and O 2- (2- should be up high and small)?
Na2(small and lower)O -Na2O
Charges must balance so 2 sodium ions are required.
What is the chemical formula of magnesium hydroxide, formed from Mg2+ and OH (2+ should be small and up higher)
Mg(OH)2 (small lower 2)
Charges must balance so 2 hydroxide ions are required.
What is a covalent bond?
A bond formed when an electron pair is shared between 2 atoms.
What forms as a result of covalent bonding?
A molecule
Draw a dot and cross diagram for the formation of methane (CH4) (little 4 at bottom)
See PMT flashcard 101
True or false?
‘Covalent bonds are weak’
FALSE
Covalent bonds are strong
Which is smaller, an atom or a molecule?
An atom.
Simple molecules consist of atoms joined by strong covalent bonds within the molecule.
Why do ionic compounds have high melting points?
Strong electrostatic attraction between the positive and negative ions requires a lot of energy to overcome.
When do ionic compounds conduct electricity?
Why?
When molten or aqueous (dissolved in water) because the ions are charged and free to move. When solid, the ions are fixed in an ionic lattice so can’t move.
Why do simple molecular compounds have low melting and boiling points?
They have weak intermolecular forces (forces between molecules) which only require a little energy to overcome.
Do simple molecular compounds conduct electricity? Why/why not?
No because there are no charged particles.
Do giant covalent structures have a high melting point? Explain your answer.
Yes because they have lots of strong covalent bonds which require a lot of energy to break.
