Chemistry: Periodic Table and Trends

Flashcards based on Chemistry lecture notes focusing on the periodic table, periodicity, atomic radius, ionization energy, and melting points of Period 3 elements.

What are the four blocks of the periodic table?

s-block, p-block, d-block, and f-block

How are elements in the periodic table arranged?

Elements are arranged according to their proton number

What is a period on the periodic table?

The horizontal rows

What is a group 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 and what elements are in each?

• S-block = g1 and 2

• P-block = g3 and 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 configurations.

What is the trend in at. radius along a period?

It decreases.

Why does at. radius decrease along a period?

• Due to an increased nuclear charge for the same number of electron shells.

• This means that the os. electrons are pulled in closer to the nuc. because the charge produces a greater attraction.

What is the trend in at. radius going down a group?

• Increases

Why does at. radius increase going down a group?

• An electron shell is added, increasing the distance between the os. electrons and the nuc. reducing the power of attraction.

• More shells also increases electron shielding

• The nuclear attraction is reduced further

What is the trend in ionisation energy along a period?

Ionization energy increases.

Why does ionization energy increase along a period?

• At. radius decreases so nuclear charge increases.

• The outer electrons are held more strongly so more energy is required to remove the os. electron and ionise the atom.

What is the trend in ionisation energy going down a group?

Ionisation energy decreases.

Why does ionisation energy decrease going down a group?

• The nuclear att. between the nucleus and os. electron reduces and shielding also increases.

• Means less energy is required to remove the oe.

What does the mp. of period 3 elements depend on?

• The structure of the element

• The bond strength

What happens to mp. across Period 3 between Na and Al?

• Na, Mg and Al are all metals with metallic bonding. Their mp. increase due to greater + charge of their ions.

• Meaning more electrons are released as delocalised electrons.

• Increases the attractive electrostatic forces from Na to Al so more energy is needed to break them.

Why does the mp. increase dramatically for Si in Period 3?

• Si has a very strong covalent structure.

• More energy is required to break the strong covalent bonds - giving it a very high mp.

Why does the mp. decrease in Period 3 between P and Cl?

• P, S and Cl are all simple covalent held with weak vdw.

• Less energy is needed to overcome these weak imf.

• hence low mp.

Why does Ar have an even lower mp than Cl?

• Ar is a noble gas that exists as individual atoms with full Os. of electrons

• Makes it very stable and the vdw. weak

• Less energy is needed to overcome vdw. so Ar exists as a gas.