atomic structure

Question 1

isotope

Answer 1

Properties of isotopes
Isotopes have similar chemical properties but different physical properties.
- Isotopes have similar electronic configuration and number of valence electrons. The chemical properties of isotopes are similar because chemical reactions involve only valence electrons.
The physical properties differ due to different relative masses of the isotopes.

Radioisotopes
- Isotopes that emit high-energy radiation are called radioisotopes.

Question 2

quantum numbers

Answer 2

principal quantum number (n)
- Takes on positive integral values of 1, 2, 3, and so forth.
- n=number of electron shells (period number)

second quantum number (l)
- number of subshells
- derived from n
- can take integral values from 0 to (n-1)
0: s
1: p
2: d
3: f

magnetic quantum number (ml)
- number of electron orbitals
- orbitals: maximum 2 electrons
- derived from l
- can take an integral value from -l to l (including 0 and 1)

Question 3

ionisation energy

Answer 3

• energy required to remove an electron from its gases atom/ion
• It measures the ease of an atom/ion losing an electron
• chemical equation: X(g) –> X + (g) + e–

1st ionisation energy:
X(g) –> X+ (g) + e– 1

2nd ionisation energy
X +(g) –> X2+(g) + e– 2

3rd ionisation energy
X2+(g) –> X3+ (g) + e– 3

more reactive metal –> lower first ionisation energy
first ionisation energy of metal x is greater than that of metal y.
- The valence electron of metal X experiences greater force of attraction from the
nucleus compared to metal Y.
- Less energy is required to remove the valence electron from metal Y atom. Metal Y is more reactive than metal X.

Question 4

trends in successive ionisation energy

Answer 4

e.g. sodium
Successive ionisation energies (IE) increase because:
After the removal of the 1st electron, a positively-charged ion is formed.
Greater amount of energy is needed to remove electrons from a cation
as compared to a neutral atom.

The two sharp increases in IE are due to the following reasons:
1st sharp increase in IE due to the removal of a 2p electron for the 2nd IE compared to the removal of a 3s electron for the 1st IE. The 2p electron is more strongly
attracted to nucleus than the 3s electron. Hence much more energy is required to
remove the 2p electron as it is from an inner electron shell.

2nd sharp increase in IE due to the removal of a 1s electron for the 10th IE compared to the removal of a 3s electron for the 9th IE. The 1s electron is more strongly attracted to nucleus than the 2s electron. Hence much more energy is required to remove the 1s electron as it is from an inner electron shell.

State with explanations the Group of the periodic table to which B is likely to belong to.
The largest increase is between the 6th and 7th ionisation energies. The 7th electron is removed from the inner principal quantum shell while the 6th electron is removed from the valence shell. Therefore, there are 6 electrons in the valence shell. Element B is in Group VI.

Write the valence electron configuration of B.
The valence electron configuration of B is ns2 np4 where n is the principal quantum
number of the valence/outermost shell.