2.1 Periodicity Flashcards
How are elements in the periodic table arranged?
By proton number
What is a period on the periodic table?
The horizontal rows
What are groups on the periodic table?
The vertical columns
What does the group number indicate on the periodic table
The number of outer electrons of an element
What are the 4 blocks of the periodic table?
S-block
P-block
D-block
F-block
What elements are in each block of the periodic table?
S-block: groups 1 and 2
P-block: groups 3 to 0
D-block: transition metals
F-block: radioactive elements
What is periodicity ?
The study of trends within the periodic table. Often these trends are linked to elements electronic configuration
What is the trend in atomic radius along a period?
Decreases
Why does atomic radius decrease across a period?
Atomic radius decreases due to an increased nuclear charge for the same number of electron shells
This means that the outer electrons are pulled closer to the nucleus because the charge produces a greater attraction
As a result the atomic radius is reduced
What is the trend of atomic radius going down a group?
Increases
Why does atomic radius increase going down a group
With each increment down the group an electron shell is added
This increases the distance between the outer electrons and nucleus, reducing the power of attraction
More shells also increases electron shielding, whereby the inner shells create a ‘barrier’ that blocks the attractive forces
The nuclear attraction is reduced further and the atomic radius increases
What is the trend in ionisation energy along a period
Increases
Why does ionisation energy increase along a period
It increases because atomic radius decreases, hence nuclear charge increases
This means that the outer electrons are held more strongly so more energy is required to remove the outer electron and ionise the atom
What is the trend in ionisation energy going down a group
Decreases
Why does ionisation energy decrease going down a group
The nuclear attraction between the nucleus and outer electrons reduces and shielding increases. Both of these factors mean less energy is required to remove the outer electron
What does the melting point of Period 3 elements depend on?
The structure of the element
The bond strength
What happens to melting points across Period 3 between sodium and aluminium?
Sodium, Magnesium and aluminium are all metals with metallic bonding.
Their melting points increase due to greater positive charge of their ions
This means more electrons are released in the form of free electrons
This increases the electrostatic attractive forces from Na to Al, therefore more energy is needed to break them
Why does the melting point increase dramatically for silicone in Period 3?
Silicon has a very strong covalent structure
So more energy is required to break the strong covalent bonds giving it a very high melting point
Why does the melting point decrease in Period 3 between Phosphorus and Chlorine
Phosphorus, Sulphur and Chlorine are all simple molecules held with weak Van de Waals forces
Less energy is needed to overcome these weak intermolecular forces, so these molecules have relatively low melting points
Why does argon have an even lower melting point than Chlorine
Argon is a noble gas that exists as individual atoms with a full outer shell of electrons
This makes the atom very stable and Van de Waals forces between them very weak
As a result less energy is needed to overcome these weak Van de Waals forces and so argon exists as a gas at room temperature
8.1 Q1) From the elements Br, Cl, Fe, K, Cs and Sb pick out:
i. In the same period
ii. In the same group
iii. That are non metals
B) one element
i. That is in the d-block
ii. That is in the s-block
i. Any two from Br, K and Fe
ii. Br and Cl or K and Cs
iii. Br, Cl
B) i. Fe
ii. K or Cs
8.1 Q2) From the elements: Tl, Ge, Xe, Sr, and W
A) a noble gas
B) the element described by Group 4, Period 4
C) an s-block element
D) a p-block element
E) a d-block element
A) Xe
B) Ge
C) Sr
D) Ge or Xe
E) W
8.2 Q1) Whereabouts in a period do you find the following? Choose from left, right or middle
A) elements that lose electrons when forming compounds
B) elements that accept electrons when forming compounds
A) Left
B) Right
8.2 Q2) In what group do you find an element that exists as the following?
A) separate atoms
B) a macromolecule
A) 0 or 8 (or 18)
B) 4
8.2 Q3) A and B are both elements. Both conduct electricity - A well, B slightly. A melts at a lower temperature, B at a much higher temperature
Suggest the identity of A and B and explain how their bonding and structure account for their properties
A: Na
B: Si
8.3 Q1) What happens to the size of the atoms as you go from left to right across a period? Choose from increase decrease and no change
Decrease
8.3 Q2) What happens to the first ionisation energy as you go from left to right across a period? Choose from increase decrease and no change
Increase
8.3 Q3) What happens to the nuclear charges of the atoms as you go from left to right across a period?
Increase
8.3 Q4) Why do the noble gases have the highest first ionisation energy of all elements in their period?
Because they have the highest nuclear charge
8.4 Q1) Write the electron arrangement in the form of 1s2….for:
A) beryllium
B) Boron
A) 1s2 2s2
B) 1s2 2s2 2p1
8.4 Q2) If one electron is lost from each of the following atoms, which main level does it come from?
A) beryllium
B) boron
A) 2s
B) 2p
8.4 Q3) Why is the first ionisation energy of boron less than that of beryllium?
Level 2p is of higher energy than 2s
8.3 The discovery of Argon
1) To how many significant figures were the two densities measured? (N2 = 1.2505g/dm3 from reaction and 1.2572 g/dm3 from removing O2 and CO2
2) using relative atomic masses from the periodic table, explain why Argon is denser than Nitrogen
3) suggest how oxygen could be removed from a sample of air
4) what would be the Mr of N3 to the nearest whole number?
5) Suggest why chemists were reluctant to regard argon as an element
1) 5
2) Ar of argon is 50% greater than that of nitrogen and 1 mole of any gas occupies the same volume
3) Pass the air over a heated metal e.g. Copper
4) 42
5) It did not fit into the periodic table as it was understood then
9.1 Q1) What is the oxidation number of all group 2 elements and their compounds
B) Explain your answer
A) +2
B) They all lose their two outer electrons when they form compounds
