Periodic table Flashcards
Definition of a group?
Vertical column in the periodic table. Elements in the same group have similar chemical properties and their atoms have the same number of outer electron shells
Definition of a period?
A horizontal row in the periodic table, Elements show trends in properties across a period
What are group 1 metals also known as?
Alkali metals
What are the group 2 metals also known as?
Alkaline Earth metals
Which is the S block
Block on left
Which is the D block?
Block in centre
Which is the P block?
Block on right
Which is the F block?
Block at bottom
What are the group 7 elements also known as?
The halogens
What are the group 8 elements also known as?
The noble gasses
Why do elements in a period show a trend in physical and chemical properties?
Due to different electronic configurations
What’s the regular repeating pattern in properties of the elements across different periods known as?
Periodicity
What’s the difference between a subshell and a orbital?
Subshell is a group of the same type of orbitals, where as an orbitals are regions of an atom containing up to 2 electrons with opposite spin
Definition of first ionisation energy?
The energy required to remove one electron from each atom in one mole gaseous atoms, to form 1 mole of gaseous +1 ions
Algebraic formula for first ionisation energy?
X(g) = X+(g) + e-
Describe the general trend in the first ionisation energy change across a period?
It increases
How does the first ionisation energy change down a group?
It decreases
Why do the first ionisation energies drop sharply when you go down a group?
The electrons are being taken away from a new outer shell, meaning the shell is further away from the nucleus, and experiences more shielding. Despite the fact the nuclear charge has increased, the nuclear attraction is still weaker, therefore less energy required to remove the outer electron
4 factors that must be used every time you explain an ionisation energy question?
Nuclear charge (amount of protons)
Sheilding (number of shells)
Atomic radius
Nuclear attraction
Write general trend in first ionisation energies across a period?
As you go across a period, the nuclear charge increases, and the atomic radius decreases.
As the electrons are in the same shell they experience the same shielding by inner electrons.
So the overall effect is an increased nuclear attraction for the outer electron as you go across a period, therefore more energy is required to overcome this attraction, so the first ionisation energy increases
Which are the points which don’t follow the general trend in first ionisation energy going across a period?
Between group 2 and 3
Between group 5 and 6
Explain the difference in first ionisaiton energy between Be (900) and B (801)? (group 2 and 3)
The fall between groups 2 and 3 marks the filling of the p subshell. In Be the outer electron is in a 2s subshell, where as in B the outer electron is in a 2p orbital
The 2p orbital in B is of higher energy, therefore experiences more shielding from inner electrons and ones from 2s subshell
So even though the nuclear charge increases by 1, the difference in shielding and energy means the nuclear attraction is weaker in B, so less energy is required to remove it’s outer electron
Explain the difference in first ionisation energy between Nitrogen (1402) and Oxygen (1314)? (group 5 and 6)
The fall between groups 5 and 6 marks the start of electron pairing in the p orbitals in the p subshell. In N the outer electron us unpaired in a 2p orbital, in O the outer electron is paired in a 2p orbital.
The paired electrons in oxygen repel slightly, making it easier to remove and electron than in Nitrogen
3 types of bonding elements in periods 2 and 3 could have?
Giant metallic lattice, giant covalent lattice, simple molecular structures
What’s the 4th type of bonding which can’t occur in periods 2 and 3?
Ionic bonding, requires 2 elements to form cations and anions
Type of structure in all period 2 and 3 elements?
Giant metallic structure
Li, Be
Na, Mg, Al
Giant covalent structure:
B,C
Si
Simple molecular structure:
N2,O2,F2,Ne
P4,S8,Cl2,Ar
Describe the trend in boiling points from group 1 to 8?
Increases from 1 to 4, but then decreases with groups 5 and 8 being much lower
Why do group 4 elements have highest melting points?
They have giant covalent structures, in which each element is covalently bonded to 4 other atoms
In order to melt them all 4 of these covalent bonds need to be broken requiring a lot of energy. Higher than Boron as it only makes 3 covalent bonds
Why do elements with diatomic molecules or single atoms have low melting/boiling points?
They only have weak intermolecular forces (London forces) holding the molecules together. Which can easily be broken
The strength of London forces relates to the number of electrons in the instantaneous dipole-induced dipole interactions, so the smaller the molecule, the lower the melting/boiling point
Why does the melting point increase from group 1 to 2 to 3?
Metallic bonding increases in strength with the number of electrons that can be present in the delocalised sea of electrons, and the charge of the metal ion. So in group 1 there will be +1 ions, where as in group 3 there are +3 ions, and there will be more delocalised electrons per ion in the structure. So there will be an increase in electrostatic attraction between the positive ions and sea of electrons, so more energy required to overcome these interactions
Why can metals conduct electricity?
Delocalised electrons can carry charge
Why does electrical conductivity increase from group 1 to 3?
Increased amount of delocalised electrons in sea of electrons