Periodicity Flashcards
What are the four categories that elements can be?
- metallic
- covalent network
- covalent molecular
- monatomic
what is structure of an element?
how particles are arranged
what is the bonding of an element?
how particles are held together
Give examples on the structure of elements
- molecular
- network
- lattice
Give examples on the bonding of elements
- covalent
- metallic
what is metallic bonding?
metallic bonding is the attraction between positive ions and a sea of delocalised electrons.
what is the strength of metals?
80 to 600 kJmol^-1
Give examples of covalent networks (first 20 elements)
boron, carbon, silicon
give examples of covalent molecular (first 20 elements)
hydrogen, carbon, nitrogen, oxygen, fluorine, phosphorus, sulfur , chlorine
give examples of metals (first 20 elements)
lithium, beryllium, sodium, magnesium, aluminium, potassium, calcium
what does a metallic structure consist of?
a metallic structure consists of a giant lattice of positively charged ions and delocalised outer electrons.
give examples of the properties of metals
- malleable (can be drawn into a sheet)
- ductile (can be drawn into a wire)
- conductors of heat
- conductors of electricity
- shiny
How are atoms in a covalent bond held together?
Held together by the electrostatic forces of attraction between positively charged nuclei and negatively charged shared electrons
What is the strength of a covalent bond?
100 to 500 kJmol^-1
name the diatomic molecules
hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine
what are the discrete molecules?
Phosphorus (P4)
Sulfur (S8)
Carbon (C60) Fullerene
what does intermolecular bonding mean?
intermolecular bonding is bonds between molecules
what does intramolecular bonding mean?
intramolecular bonding is bonds within a molecule
what is the strength of London dispersion forces?
1 to 20 kJmol^-1
What does a covalent molecular structure consist of?
discrete molecules held together by weak intermolecular forces.
What are the properties of discrete covalent molecules?
- Low melting and boiling points
- Soft solids
- Brittle
- Do not conduct electricity
What does a covalent network structure consist of?
A giant network of covalently bonded atoms
What are some examples of covalent network structure?
diamond, graphite (carbon), boron and silicon
What are some of the properties of diamond?
- They do not conduct (no delocalised electrons)
- Have high melting and boiling points
- Hard
- Transparent (‘tunnels’ between atoms allow light to pass through)
What are some of the uses of diamond?
cutting tools and gemstones
What are some of the properties of graphite?
- Layers separate easily
- Conducts electricity (delocalised electrons between layers)
- Have weak bonding between layers and strong bonding within layers
What are some of the uses of graphite?
pencils, lubricant, electric motors
What does a monatomic structure consist of?
Discrete atoms held together by London dispersion forces.
What are London dispersion forces?
London dispersion forces are forces of attraction which can operate between all atoms and molecules.
Note: London dispersion forces are much weaker than all other types of bonding.
What is the name of elements in group 1 of the periodic table?
Alkali metals
What is the name of elements in group 2 of the periodic table?
Alkali earth metals
What is the name of elements in group 7 of the periodic table?
Halogens
What is the name of elements in group 0/8 of the periodic table?
Nobel gases
How do London dispersion forces form?
London dispersion forces form between atoms when there is an uneven distribution of electrons in an atom. This causes one side of the atom being slightly positive and the other side slightly negative. This atom is know as a temporary dipole. When a temporary dipole is near another atom it causes the electrons in that atom to shift due to the slightly positive and negative sides. This is know as an induced dipole and this forms a London dispersion force between the atoms.
In easier terms, what are London dispersion forces a result of?
An electrostatic attraction between temporary and induced dipoles cause by movement of electrons in atoms and molecules.
What is the strength of London dispersion forces related to?
The number of electrons in an atom or molecule.
What is the relationship between the number of electrons and the strength of London dispersion forces?
The greater the number of electrons, the stronger the London dispersion forces are.
Why is there an increase in melting and boiling points going down group 7 and 0?
Because as you go down group 7/0 the number of electrons increase meaning the strength of the London dispersion forces are greater which causes an increase in melting and boiling point.
What happens to the number of full energy levels when going down a group?
They increase
What happens to the number of protons and number of electrons when going across a period?
The number of protons increase and the number of electrons also increase.
What is a period in the periodic table?
A period is a row in the periodic table.
What is a group in the periodic table?
A group is a column in the periodic table.
What is the bond length?
The bond length is the distance between the nuclei of covalently bonded atoms.
What is the covalent radius?
The covalent radius of an element is half the distance between the nuclei of two of its covalently bonded atoms.
Why is no covalent radii given for group 0?
Group 0 is monatomic and can therefore not bond to another atom.
What happens to atomic size/covalent radius as you go down a group?
The atomic size/covalent radius increases down a group because one more energy level is occupied by electrons in each element going down the group.
What happens to atomic size/covalent radius as you go across a period?
The atomic size/covalent radius decreases across a period because there is an increase in nuclear charge which pulls the outer electrons closer to the nucleus hence the decrease in atomic size/covalent radius.
What is the first ionisation energy?
The first ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms.
What does the second and subsequent ionisation energies refer to?
The energy required to remove further moles of electrons.
What is the equation of the first ionisation energy?
E(g) —–> E^+(g) + e^-
What is the equation of the second ionisation energy?
E^+(g) —–> E^2+(g) + 2e^-
What happens to the ionisation energy as you go down a group?
The ionisation energy decreases down a group because the distance between the nucleus and outer electrons increase. The extra full energy levels screen the outer electrons from the nuclear charge making it easier to remove an outer electron.
What happens to the ionisation energy as you go across a period?
The ionisation energy increases going across a period because the increased nuclear charge hold the outer electrons more tightly and closer to the nucleus making is more difficult to remove an outer electron.
Why is there sometimes a sudden jump in the value of ionisation energy.
More energy is required to remove an electron from an inner energy level that is closer to the nucleus.
What is the definition of electronegativity?
Electronegativity is a measure of the attraction an atom involved in a bond has for the electrons of that bond
What happens to the electronegativity as you go down a group?
The electronegativity decreases down a group because the atomic size increases. This means the distance between the bonding electrons and the nucleus increases and also the full inner energy levels shield the nuclear charge from the bonding electrons.
What happens to the electronegativity as you go across a period?
The electronegativity increases across a period because there is an increased nuclear charge which increases the attraction for the bonding electrons.
