Year 9 - Structure and Bonding
This is a revision of bonding and structures (Section 1) . You will need to know this for the end of year test.
Terms in this set (34)
What is an ion?
An atom with a charge
How are ions formed?
By the loss or gain of electrons
What is oxidation and reduction?
OILRIG: Oxidation Is Loss of electrons Reduction Is Gain of electrons
Do metal atoms form positive or negative ions?
Metal atoms lose electrons to form positive ions
Do non-metal atoms form positive or negative ions?
Non-metal atoms gain electrons to form negative ions
How can you deduce the charge of an ion from the electronic configuration of the atom?
All atoms want to have a full outer shell:
1) Look up the number of electrons in the outer shell
2) Metal atoms lose electrons to form positive ions, i.e. Mg, 2 electrons in its outer shell, Mg²+
3) Non-metal atoms gain electrons to form negative ions i.e. N, 3 electrons in outer shell, N³-
How can you use the periodic table to help you remember charges on ions?
Look at the group number:
Group 1 form +1 ions
Group 2 = +2
Group 3 = +3
Group 4 = +4 or -4
Group 5 = -3
Group 6 = -2
Group 7 = -1
Group 0 don't form ions
What is ionic bonding?
A strong bond between a metal and non-metal held together by the electrostatic attraction of oppositely charged ions (positive & negative ions attract)
What are some of the properties of ionic compounds?
Solids, brittle, high melting & boiling points, often soluble in water
Why do ionic compounds have high melting and boiling points?
Because the strong electrostatic forces between the oppositely charged ions take a lot of energy to overcome
Draw a dot and cross diagram showing the formation of an ionic compound (NaCl).
What is a covalent bond?
A bond formed between two non-metals by electrostatic attraction between the positive nuclei and a shard pair of electrons
How is a covalent bond formed?
A pair of electrons is shared between two atoms
What holds a covalent bond together?
The strong attraction between the shared pair of electrons and the nuclei of the atoms involved.
Draw a dot and cross diagram of the bonding in hydrogen (H₂)
Draw a dot and cross diagram of the bonding in ethene (C₂H₄)
Draw a dot and cross diagram of the bonding in ammonia (NH₃)
Draw a dot and cross diagram of the bonding in hydrogen chloride (HCl)
Draw a dot and cross diagram of the bonding in methane (CH₄)
What are the two types of covalent structures?
Giant and simple covalent structures
What are the properties of simple covalent compounds?
Gases, liquids (with low boiling points) or solids (with low melting points), they don't conduct electricity
Why do simple covalent compounds have low melting and boiling points?
Because they have weak forces of attraction between their molecules that take little energy to overcome.
What are the properties of giant covalent structures?
Solids with high melting and boiling points.
Why do giant covalent structures have high melting and boiling points?
To melt or boil you need to separate the atoms in these structures. They are held together by many strong covalent bonds which require a lot of energy to break.
What are some examples of giant covalent structures?
Diamond, graphite (both forms of carbon), silicon dioxide (sand)
What are some examples of simple covalent structures?
water, ammonia, methane, oxygen, hydrogen, chlorine, ethene, nitrogen, carbon dioxide, hygrogen chloride, ethane (can you draw a dot and cross diagram of them all?)
Describe the structure of diamond and graphite.
Diamond-each carbon atom forms 4 covalent bonds forming a rigid, giant structure
Graphite-each carbon only forms 3 covalent bonds, creating layers which can slide over each other
Why is diamond used as a cutting tool and graphite as a lubricant?
Diamond-rigid giant structure makes it very hard
Graphite-contains layers that slide over each other
Describe the structure of a metal
A giant structure of positive metal ions surrounded by a sea of delocalised electrons
What are delocalised electrons?
Why do covalent compounds not conduct electricity?
They have no free electrons or ions (exception graphite)
Do ionic compounds conduct electricity?
Yes, but only when molten or in solution. The ions are then free to move.
Why doesn't diamondⁿ conduct electricity?
Diamond doesn't conduct electricity because all four valence electrons are used to form bonds, there are no delocalised electrons
Why does graphite conduct electricity?
Graphite conducts electricity because only three valence electrons are used to form covalent bonds, the fourth electron is delocalised between the layers and free to move.
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