Periodicity

Question 1

the trend in atomic radius across period 3

Answer 1

atomic radius decreases across a period

because the increased number of protons results in increase nuclear charge.
- similar shielding effect as outer electrons are all in the same energy levels

Question 2

define first ionisation energy

Answer 2

-The energy needed to remove one mole of electrons from one mole of atoms in their gaseous state to form one mole of 1+ (also in their gaseous state)

Question 3

define successive ionisation energy

Answer 3

-removal of more than 1 electron from the same atom

Question 4

trend in 1st ionisation energy across period

Answer 4

• increases across the period as the nuclear charge increases
  -similar shielding
  -greater attraction between the nucleus and outer electron
• atomic radius increases

Question 5

why is there a small drop Mg + Al.

Answer 5

-outer electron of Mg is in the orbital 3s, whereas Al is in 3p.

-3p electron has more energy than the 3s electron, so the ionization energy of Al is actually less than Mg.

-because the 3p electron requires less energy to be removed from the atom

Question 6

why is there a small drop between phosphorous and sulfur

Answer 6

-electrons in the 3p orbital in phosphorus is not paired

• electrons in the 3p orbital in sulphur are paired.

-there is a slight repulsion between the two negatively charged electrons which makes the second electron easier to remove.

Question 7

describe the melting + boiling point of Na,Mg and Al

Answer 7

• Metallic bonding

-strong electrostatic attraction between the positive ions and the delocalised electrons.

-more energy needed to break the bonds

Question 8

describe the melting and boiling point of Si

Answer 8

Si is Macromolecular
many strong covalent bonds between
atoms,
lots of energy needed to break the covalent bonds
very high mp +bp

Question 9

describe the melting and boiling point of Cl2, S8, P4

Answer 9

simple molecular
weak van Der Waals between molecules
so less energy needed to break
low mp and bp

Question 10

why does S8 have a higher mp than P4

Answer 10

because it has more electrons
so has stronger van der waals between molecules

Question 11

describe the trend in electronegativity across period 3

Answer 11

-increases across period
-atomic radius decreases, nuclear charge increases
-greater attraction between the electron and nucleus