Ionic and Covalent Bonding Flashcards
Describe the formation of cations.
when an atom loses electron(s)
Are metals always cations or anions?
cations
What is a cation?
positively charged ions
What is an anion?
negatively charged ions
Describe the formation of anions.
when an atom gains electron(s)
What is the relationship between group number and the charge of ions formed from that group?
usually, elements form cations which charge = group number
usually, elements form anions which charge = 8 - group number
(transition metals have variable oxidation numbers)
What are the oxidation numbers of transition metals?
variable oxidation numbers
What type of elements have variable oxidation numbers?
transition elements
What is an ionic bond?
a strong electrostatic attraction between oppositely charged ions
Describe the properties of ionic compounds.
- high melting points and boiling points
- good electrical conductivity when aqueous or molten and poor when solid
Describe the giant lattice structure of ionic compounds.
a regular arrangement of alternating positive and negative i ons
Ionic compounds are arranged in…
giant lattice structures
Ionic bonds are formed between _____.
metals and non-metals
Metals and non-metals form…
ionic bonds
Why do ionic substances have high melting/boiling points?
electrostatic forces holding ions together are very strong, a lot of energy needed to separate the ions
Why do ionic substances only conduct when molten or aqueous, not solid?
- ions in solid unable to move freely (conduction of electricity occurs when ions can move freely, carrying charge)
- in molten/aqueous solution, ions are free to move and carry charge
When is a covalent bond formed?
when a pair of electrons is shared between atoms leading to noble gas electronic configurations
What is a covalent bond?
a shared pair of electrons
A covalent bond forms between ______.
two non-metals
Two non-metals bond ______.
covalently
What are properties of simple molecular compounds (covalent)?
- low melting/boiling points
- poor electrical conductivity
Why do simple covalent compounds have low melting/boiling points?
weak intermolecular forces between molecules
Why do simple covalent compounds not conduct electricity?
no overall charged particles in molecules which can move freely through the structure
In covalent molecules, how does size affect melting/boiling points?
the larger the molecule, the higher the melting/boiling point: greater number of weak intermolecular forces between molecules, which need more energy
to overcome
Describe the structure of diamond.
Describe the structure of graphite.
- layered hexagonal arrangement: each layer is a macromolecule
- layers held together by many weak intermolecular forces
- three of the electrons from each C atom are in covalent bonds
- fourth electron leaves atom, forming a layer of delocalised electrons above the atoms
Graphite and diamond are both made out of which element?
carbon
Graphite and diamond are both ______ structures.
giant covalent
Name two giant covalent structures.
graphite and diamond
Why is graphite soft and slippery?
layers slide over each other (weak intermolecular forces)
Why is graphite used as a lubricant?
it is soft and slippery because its layers slide over one another
Graphite has lots of layers that can slide over one another. Which property of graphite results from this structure?
soft and slippery
Why is graphite used as an electrode?
excellent electrical conductor, inert and high melting/boiling points
Why is diamond used in cutting tools?
nothing is harder than diamond: it is made up of many strong covalent bonds in a giant structure
1 use of diamond
cutting tools
2 uses of graphite
lubricant
electrode
Describe the giant covalent structure of silicon(IV) oxide.
each Si atom has four electrons in the outer shell, making 4 covalent bonds w/ oxygen to obtain a full outermost shell
Describe the similarity in properties between diamond and silicon(IV) oxide. Why is this?
- form transparent crystals
- very hard (made from many strong covalent bonds in a giant structure)
- extremely high melting + boiling points
- do not conduct electricity (no delocalised electrons)
- do not dissolve in water (no charged particles)
Why do both diamond and silicon (IV) oxide not conduct electricity?
there are no delocalised electrons which can move
Why do both diamond and silicon (IV) oxide not dissolve in water?
no charged particles
Why are both diamond and silicon (IV) oxide very hard?
they are made from many strong covalent bonds in a giant structure
Which two giant covalent substances are very similar in terms of their properties?
diamond and silicon (IV) oxide
