2.1 Periodicity
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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