Topic 2 Flashcards
(31 cards)
How are ions formed?
When electrons are transfered.
Are all metals positive or negative ions?
When metals form ions they lose electrons becoming a positive ion (cations)
When non metals become ions are they negative or postive?
They gain electrons to become a negative ions (anions)
If an atom loses 2 electrons what is the charge on the ion?
2+
What are the groups most likely to form ions and why?
1,2 and 6,7. This is because they only need to gain or lose 1 or 2 electrons to gain a full outer shell.
When a metal and non metal react together what is it called?
Ionic bonding.
Why are ionic compounds strongly attracted?
As the metal atom loses electrons to form a positively charged ion and the non metal gains an electron to become a negatively charged ion. These oppositely charged ions are strongly attracted by electrostatic forces.
What is one pro and one con of a dot and cross diagram?
They show the transfer of electrons.
However, they don’t show how ions are arranged in 3d.
Does Not show relative sizes of the ions.
What is ionic compounds structure called?
ionic lattice. The ions are closely packed and have strong electrostatic forces of attraction.
What are some properties of ionic compounds?
Have high melting points and High boiling points - Due to strong electrostatic attraction between oppositely charged ions. Therefore needs large amounts of energy to overcome.
Conducts electricity when melted or dissolved in water. - Because ions are free to move can carry charge.
Does not conduct electricity when solid.
Define covalent bonding.
A bond formed when electrons are shared between non-metal atoms.
Why are covalent bonds very strong?
The positively charged nuceli of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces making them very strong.
What are simple molecular substances?
Substances made of up of molecules containing few atoms joined together by covelent bonds.
What are some properties of simple molecular substances and why?
Small molecules are usually gases or liquids and have relatively low melting and boiling points examples are water. - When boiling or melting substances made of small molecules, the weak intermolecular forces between molecules are overcome and not the strong covalent bonds between molecules. This does not require much energy.
Small molecules do not conduct electricity as they have no charge.
Bigger molecules have stronger intermolecular forces so have higher melting + boiling points.
What are polymers and what are properties of them?
Polymers are very large molecules made up of many long chains of repeating units joined by covalent bonds.
Polymer chains are held together by intermolecular forces. Because polymers are very long molecules these intermolecular forces are relatively strong. Meaning they have higher melting points compared to smaller molecules. Solid at room temp.
What are the properties of Giant covalent structure?
High melting points - Many strong covalent bonds have to be broken requiring lots of energy.
All atoms in a giant covalent structure are bonded to other atoms by strong covalent bonds.
Most do not conduct electricity except graphite - They have no delocalised electrons or ions that are free to move to carry charge.
What are the main three examples of Giant Covelent Structure and what is the structure of each one?
Diamond (Each carbon forms four strong covalent bonds.)
In Graphite (Each carbon atom forms three covalent bonds, each carbon also has one delocalised electrons.)
Silicon dioxide is one giant structure of silicon and oxygen.
What is a allotrope?
Allotropes are diffrent structural forms of the same element in the same physical state.
Why are diamonds hard?
Due to each carbon strongly covalently bonded to 4 other carbon atoms. Therefore requires lots of energy to break.
What is a fullerene?
Fullerenes are molecules of carbon shaped likes closed tubes or hollow balls.
Fulerenes can be used to cage other molecules. What is one use of a fullerene?
Drug delivery Industrial catalysts due to huge surface area. Great lubricants
What is a nanotube and some properties?
Tiny carbon cylinder. They conduct electricity and heat. High tensile strength (don’t break when streched.)
Why can metals conduct electricity and thermal energy?
As they have delocalised electrons that can carry charge between the layers.
Metals are good conductors of thermal energy because they have delocalised electrons that transfer energy.
Why is metallic bonding so strong?
As there are strong electrostatic forces of attraction between the positive metal ions and the shared negative electron.
