Chemistry - Atoms, Bonds and Groups - F321 - Electrons, Bonding and Structure (2) Flashcards
Define the first ionisation energy of an element.
The first ionisation energy of an element is the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.
What are plasma televisions made from?
Plasma televisions are made of a mixture of positive and negative ions.
What provides evidence that electrons are arranged in shells?
Ionisation energies provide evidenve that electrons are arranged in shells.
Which electrons are removed first?
Electrons in the outer shell are removed first as they experience the least attraction to the nucleus.
The nuclear attraction experienced by an electron depends on…:
The nuclear attraction experienced by an electron depends on:
- atomic radius
- nuclear charge
- electron shielding
Define electron shielding
Electron shielding is the repulsion between electrons in different inner shells. Shielding reduces the net attractive force from the positive nucleus to the outer-shell electrons.
How many ionisation energies does each element have?
Each element has as many ionisation energies as it does electrons.
TRUE or FALSE
Each successive ionisation energy is smaller than the one before.
FALSE!
Each successive ionisation energy is larger than the one before.
What does a large difference in ionisation energies show?
A large difference n ionisation energies shows the electron has been removed from the next shell.
Define a shell.
A shell is a group of atomic orbitals with the same principle quantum number, n. Also known as a main energy level.
Define principle quantum number.
Principle quantum number, n, is a number representing the relative overall energy of each orbital, which increases with distance from the nucleus. The group of orbitals with the same n-value are referred to as electron shells or energy levels.
How many electrons can be held in the first shell?
2 electrons can be held in the first shell.
How many electrons can be held in the second shell?
8 electrons can be held in the second shell.
How many electrons can be held in the third shell?
18 electrons can be held in the third shell.
How many electrons can be held in the fourth shell?
32 electrons can be held in the fourth shell.
What is the formula for the number of electrons in each shell?
2n^2 electrons
Define an atomic orbital.
An atomic orbital is a region within an atom that can hold up to two electron with opposite spins.
What shape is an s-orbital?
An s-orbital has a spherical shape.
How many electrons can each orbital hold?
Each orbital can hold 2 electrons.
Define a sub-shell.
A sub-shell is a group of the same type of atomic orbitals (s, p, d, f) within a shell.
Electron configuration can be worked out using what principle?
Electron configuration can be worked out using the Aufbau principle.
What are the key points of working out electron configuration according to the rules of the Aufbau principle?
- electrons are added one at a time to ‘build up’ the atoms
- the lowest available energy level is filled first
- each energy level must be full before the next higher energy level starts to fill
The ……. the principle quantum number, n, the further the shell from the nucleus.
The higher the principle quantum number, n, the further the shell from the nucleus.
What are the only six elements that exist as unbonded atoms?
Helium Neon Argon Krypton Xenon Radon
The noble gases.
Noble gases make up what percentage of the air?
Noble gases make up ~1% of the air.
What is the most abundant noble gas in the air?
Argon is the most abundant noble gas in the air.
What is the use of helium?
Helium is used in airships.
What is the use of neon?
Neon is used in advertising signs.
What is the use of argon?
Argon is used in filament lightbulbs.
What is the use of krypton?
Krypton is used in lasers for eye surgery.
What is the use of xenon?
Xenon is used in car headlights.
Define an ionic bond.
An ionic bond is the electrostatic attraction between oppositely charged ions.
Define a giant ionic lattice.
A giant ionic lattice is a three-dimensional structure of oppositely charged ions, held together by strong ionic bonds.
How do all ionic compounds exist in their solid state?
All ionic compounds exist as a giant ionic lattice in the solid state.
Elements in the same …. of the periodic table have the same number of outer shell electrons and react in similar ways.
Elements in the same group of the periodic table have the same number of outer shell electrons and react in similar ways.
Define a group in the periodic table.
A group is a vertical column in the periodic table. Elements in the same group have similar chemical properties and their atoms have the same number of outer shell electrons.
Which atoms do not usually form ions?
Beryllium, boron, carbon and silicon do not normally form ions as too much energy is needed to transfer the outer shell electrons to form ions.
Define a covalent bond.
A covalent bond is a bond formed by a shared pair of electrons.
Define a lone pair.
A lone pair is an outer shell pair of electrons that is not involved in chemical bonding.
Define a dative covalent bond.
A dative covalent bond or coordinate bond is a shared pair of electrons which has been provided by one of the bonding atoms only.
What is anothe rname for a dative covalent bond?
A dative covalent bond is also known as a coordinate bond.
How can a dative covalent bond be written?
A –> B
Where the arrow represents which atoms has donated a lone pair of electrons to form the dative covalent bond.
When an acid is added to water, what ions does the water form?
When an acid is added to water, the water forms oxonium ions H3O+
What shape will a molecule with three electron pairs around the central atom form?
A molecule with three electron pairs around the central atom will have a trigonal planar shape.
What shape will a molecule with four electron pairs around the central atom form?
A molecule with four electron pairs around the central atom will have a tetrahedral shape.
What shape will a molecule with six electron pairs around the central atom form?
A molecule with six electron pairs around the central atom will have an octahedral shape.
What is the bond angle in a molecule of trigonal planar shape?
The bond angle in a molecule of trigonal planar shape is 120o
What is the bond angle in a molecule of tetrahedral shape?
The bond angle in a molecule of tetrahedral shape is 109.5o
What is the bond angle in a molecule of octahedral shape?
The bond angle in a molecule of octahedral shape is 90o
How much does each lone pair reduce the bond angle by?
Each lone pair reduces the bond angle by ~2.5o
Define electronegativity.
Electronegativity is a measure of the attraction of a bonded atom for the pair of electrons in a covalent bond.
A charge difference between two bonded atoms such as H-Cl is called what?
A charge difference between two bonded atoms such as H-Cl is called a permanent dipole.
Define a permanent dipole.
A permanent dipole is a small charge difference across a bond that results from a difference in the electronegativities of the bonded atoms.
What scale is used to measure electronegativity?
The Pauling scale is used to measure electronegativity.
At room temperature, all ionic compounds are what?
At room temperature, all ionic compounds are solid.
Define an intermolecular force
An intermolecular force is an attractive force between neighbouring molecules.
What are the three types of intermolecular force?
The three types of intermolecular force are:
- Hydrogen bonds
- Permanent dipole -dipole
- van der Waals’
Define van der Waals’ forces.
van der Waals’ forces are attractive forces between induced dipoles in neighbouring molecules.
What causes can der Waals’ forces?
van der Waals’ forces are caused by the movement of electrons in shells.
What increases the number/strength of van der Waals’ forces?
van der Waals’ forces increase with the number of electrons.
What are the only attractive intermolecular forces that act between non-polar molecules?
van der Waals’ forces are the only attractive intermolecular forces acting between non-polar molecules.
What percentage of the strength of a covalent bond is an hydrogen bond?
An hydrogen bond is about 5% of the strength of a covalent bond.
Why do hydrogen bonds make ice less dense than water?
Hydrogen bonds make ice less dense than water because hydrogen bonds hold the water molecules apart so ice has an open lattice structure that collapses as it melts.
Define metallic bonding.
Metallic bonding is the electrostatic attraction between positive metal ions and delocalised electrons.
Delocalised electrons are shared between how many atoms?
Delocalised electrons are shared by more than two atoms.
Define a giant metallic lattice.
A giant metallic lattice is a three-dimensional structure of positive ions and delocalised electrons, bonded together by strong metallic bonds.
When are ionic compounds conductors of electricity?
When melted or dissolved in water ionic compounds are conductors of electricity.
Ionic lattices dissolve in what?
Ionic lattices dissolve in polar solvents.
Define a simple molecular lattice.
A simple molecular lattice is a three-dimensional structure of molecules, bonded together by weak intermolecular forces.
Are simple molecular lattices conductors of electricity?
Simple molecular lattices are non-conductors of electricity.
Do simple molecular lattices have relatively high or low boiling and melting points?
Simple molecular lattices have relatively low melting and boiling points.
What are simple molecular lattices soluble in?
Simple molecular lattices are soluble in non-polar solvents (eg hexane).
Define a giant covalent structure.
A giant covalent structure is a three-dimensional structure of atoms, bonded together by strong covalent bonds.
What molecules have giant covalent structures?
Graphite and diamond have giant covalent structures.
What shape is diamond?
Diamond has a tetrahedral structure.
What shape is graphite?
Graphite has a hexagonal layer structure.
