Final answer:
a) The electron configuration of oxygen is 1s² 2s² 2p⁴. b) The principal quantum number determines the size and energy of an orbital. c) Atoms and ions differ in size due to the number of electrons they have. d) Energy levels determine the distribution of electrons in an atom.
Step-by-step explanation:
a) The electron configuration of oxygen can be written as 1s2 2s2 2p4. This means that oxygen has 2 electrons in the 1s orbital, 2 electrons in the 2s orbital, and 4 electrons in the 2p orbital.
b) The principal quantum number, represented by 'n', is a measure of the energy level and distance from the nucleus. It determines the size and energy of an orbital. As 'n' increases, the size and energy of the orbital also increase.
c) When atoms form ions, they gain or lose electrons to achieve a stable electron configuration. The size of an ion is determined by the number of electrons it has. Anions, which are negatively charged ions, have more electrons compared to their parent atoms, making them larger. Cations, which are positively charged ions, have fewer electrons compared to their parent atoms, making them smaller.
d) Energy levels represent the different energy states that electrons can occupy in an atom. The electron distribution refers to the arrangement of electrons in these energy levels and orbitals. Electrons fill the lower energy levels first before filling higher energy levels. The number of electrons in each energy level corresponds to the principal quantum number.