C8. Periodicity

Question 1

How are elements in the periodic table arranged?

Answer 1

Atomic number

Question 2

What are the trends in elements of a group?

Answer 2

Group (Collum); Similar chemical properties; Same number of electrons in valence shell

Question 3

What are the trends in periods?

Answer 3

Periods (rows); Same principal quantum number (electron shells);

Question 4

What are the blocks and what do they convey?

Answer 4

S, D, P, F ; Which orbital the furthest electron occupies

Question 5

What is the trend across period 3?

Answer 5

Atomic radius decreases; Increased nuclear charge, pulls valence shell closer; Shielding effect is similar;

Question 6

What is the trend in melting points for metals across period 3?

Answer 6

Increase; Metal ions, increasing positive charge, increasing number of delocalised electrons, smaller ionic radius, as a result a stronger metallic bond

Question 7

What element has the highest melting point in period 3 and why?

Answer 7

Silicon; Giant covalent macromolecular structure; Many strong covalent bonds; Large amount of energy needed to overcome many strong covalent bonds

Question 8

What is the trend in melting points of the period 3 elements P, S, Cl, Ar?

Answer 8

P4, lower melting point than Si; Weaker molecular structure, weak van der waal force;
S8, higher melting point than P4; larger simple molecular structure; larger van der waal forces;
Cl2, much lower melting point than S8; smaller simple molecular structure; smaller van der waal forces;
Ar, lower melting point than Cl2; Lowest melting point due to existing as an individual atom; Smaller van der waal forces

Question 9

What is the definition of ionisation energy?

Answer 9

Minimum energy required to remove one mole of electrons from one mole of atoms in gaseous state.

Question 10

What is the equation of first ionisation of Sodium?

Answer 10

Na(g) => Na+(g) + e-

Question 11

Why is first ionization energy always positive?

Answer 11

Requires energy, endothermic process; 495.8kj mol-1

Question 12

What factors increase first ionisation energy?

Answer 12

Less shielding; Higher nuclear charge, more protons in nucleus; Smaller atom size, attractive forces between valence electron and nucleus increases;

Question 13

What is successive ionisation?

Answer 13

Removal of more than one electron from the same atom

Question 14

What is the trend of first ionisation energy down a group ?

Answer 14

Decreases; Atomic radius increases, attraction to nucleus decreases; Shielding increases, shields attractive force between nucleus and valence electron

Question 15

What data provides strong evidence for shells in atoms in Neil Bohr’s model?

Answer 15

First ionisation energy decreasing down a group due to shielding

Question 16

What is the trend of first ionisation energy across a period?

Answer 16

Increase; Nuclear charge increases; Shielding stays similar; Atomic radius decreases

Question 17

Why does Aluminium have a lower first ionisation energy than Magnesium?

Answer 17

Al valence electron, 3P1 subshell; Mg valence electron, 3S2; Higher energy subshell, further from nucleus, 3S2 shell provides slight shielding

Question 18

What data is proof of subshells existing?

Answer 18

Aluminium having lower first ionisation energy than Magnesium

Question 19

What data is proof of electron repulsion in orbitals?

Answer 19

Sulfur having lower first ionisation energy than Phosphorus

Question 20

Why does Sulfur have lower first ionisation energy than Phosphorus?

Answer 20

S valence electron, 3P2; P valence electron 3P1; Electrons repel each other in an orbital; Easier to remove S’s 3P2 electron