Electrons, bonding and structure Flashcards
What is the characteristic shape of an s orbital?
Circular
What is the shape of a p orbital?
3 figure 8’s on top of each other
What are the levels of shells and orbitals and the number of electrons
1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10
Describe ionisation.
The removal of one or more electrons
What is first ionisation energy?
The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions
Is ionisation endothermic r exothermic?
Endothermic, you have to put energy in.
How would you write an equation for the first ionisation energy of oxygen?
O(g) ➡️ O+ (g) + e-
How does nuclear charge affect ionisation?
The more protons there are in the nucleus, the more positively charged the nucleus is and the stronger the attraction for the electrons
How does distance from the nucleus affect ionisation energy?
Attraction falls off very rapidly with distance. An electron close to the nucleus will be much more strongly attracted than one further away.
How does shielding affect ionisation energy?
As the number of electrons between the outer electrons and the nucleus increases, the outer electrons feel less attraction towards the nuclear charge. This lessening of the pull of the nucleus by inner shells of electrons is called shielding.
What is meant by saying something has a high ionisation energy?
There is a high attraction between the electron and the nucleus.
What is the definition for the second ionisation energy?
The second ionisation energy is the energy needed to remove 1 electron from 1 mole of gaseous 1+ ions to form one mole of gaseous 2+ ions
How do successive ionisation energies vary within each cell?
Within each cell, successive ionisation energies increase. This is because electrons are being removed from an increasingly positive ion. There is less repulsion amongst the remaining electrons, so they are held more strongly by the nucleus.
What does a big jump on an ionisation energy graph signify?
A new shell being broken into, an electron is being removed from a shell closer to the nucleus
How can you tell from an ionisation graph what group an element is from?
The number of electrons before the first big jump will indicate the group of the element.
What causes ionic bonding?
Electrostatic attraction
How are ions formed?
When an electron is transferred from one element to another
Name four compound ions.
Nitrate - No3- Carbonate - CO3(2-) Sulfate - SO4(2-) Ammonium NH4+
What is an ionic bond
An electrostatic attraction between two oppositely charged ions
Give two examples of ionic compounds
Sodium chloride and magnesium oxide
What kind of diagram do you use to show ionic compounds?
Dot and cross but with brackets around them to show the ionisation
What is the structure of sodium chloride?
Giant ionic lattice
Why is sodium chlorides structure a giant ionic lattice?
The ionic bonds are very strong so it takes a lot of energy to break up the lattice.
Do ionic compounds conduct electricity? Why?
They do when they are molten or dissolved but not when they are solid
The ions in a liquid are free to move (and they carry a charge)
In a solid they are fixed in position by strong ionic bonds
What is the melting point of ionic compounds? Why?
They have high melting points, the giant ionic lattices are held together by strong electrostatic forces. It takes loads of energy to overcome these forces, so melting points are very high.
Are ionic compounds soluble?
Generally yes, water molecules are polar. Part of the molecule has a small negative charge, and the other bits have small positive charges. The water molecules pull the ions away from the lattice and cause it to dissolve.
Describe covalent bonding
This is when atoms share electrons with one another so they’ve all go full outer shells.
How are covalent bonds drawn?
Dot and cross diagrams
Give two examples of giant covalent lattices
Diamond and graphite
What is a giant covalent lattice?
Huge networks of covalently bonded atoms
What kind of structure is diamond?
A giant covalent lattice, the hardest known substance
What are the chemical properties of diamond? (5)
- very high melting point
- extremely hard
- vibrations travel easily through the stiff lattice so it’s a good thermal conductor
- it can’t conduct electricity - all the outer electrons are held in localised bonds
- it wound dissolve in any solvent
How do the bonds in graphite affect the function?
- weak bonds between the layers in graphite are easily broken, so the sheets can slide over each other, graphite feels slippery and is used as a dry lubricant and in pencils
What kind of bond is present in graphite?
Weak van der waals forces
What is the structure of graphite?
Sheets of flat hexagons covalently bonded with three bonds each, fourth electron is delocalised and sheets are bonded together by weak van der waals
How can electric current flow through graphte?
Delocalised electrons are t attached to any particular carbon atom and are free to move along the sheets, so an electric current can flow
What is the melting point of graphite?
It is high because of the strong covalent bonds (over 3900k)
Can graphite be dissolved in water?
No because the covalent bonds In the sheets are too difficult to break
How are metals structured?
They exist as giant metallic lattice structures,
The electrons in the outermost shell of an atom are delocalised. Free to move about the metal. This leaves a positive metal ion. These are attracted to delocalised negative electrons. They form a lattice of closely packed positive ions in a sea of delocalised electrons.
Describe the melting point of metals.
The number of delocalised electrons per atom affects the melting point. The more there are, the stronger the bonding so the higher the melting point. The size of the metal ion and the lattice structure also affect the melting point
Describe the bonding in metals
There are no bonds holding specific ions together, the metal ions can slide past each other when the structure is pulled so metals are malleable and ductile.
Are metals soluble?
No they are not, except for liquid metals because if the strength of the metallic bonds
Can metals conduct heat and electricity?
Yes because the delocalised electrons can carry current and pass kinetic energy on
Do shells have more energy if they are far away from the nucleus or close to it?
Further away from the nucleus
