A LEVEL CHEMISTRY QUESTIONS AND ANSWERS 2025

A LEVEL CHEMISTRY QUESTIONS AND ANSWERS 2025


QUESTION: Element - ANSWER-A pure substance made of only one kind of atom




QUESTION: Atom - ANSWER-Smallest particle of an element




QUESTION: Proton - ANSWER-Positively charged particle in the nucleus of an atom




QUESTION: Neutron - ANSWER-Uncharged particle in the nucleus of an atom




QUESTION: Electron - ANSWER-Negatively charged particle in orbitals outside the nucleus of an atom.




Has negligible mass compared to a proton.




QUESTION: Energy levels - ANSWER-The specific distances from the nucleus corresponding to the
energy of the electrons.




Electrons in energy levels further from the nucleus have more energy than those closer.




Split up into sub-levels s, p, d, etc.

,QUESTION: Anode - ANSWER-Positive electrode, where oxidation occurs.




QUESTION: Masses and charges of subatomic particles - ANSWER-Relative mass:

• Electron (e-): 1/1836

• Neutron (n): 1

• Proton (p): 1




Relative charge:

• Electron (e-): -1

• Neutron (n): 0

• Proton (p): 1




QUESTION: Atomic (proton) number - ANSWER-Number of protons.




Subscript in isotopic notation.




QUESTION: Isotope - ANSWER-Atoms of the same element that have different numbers of neutrons




QUESTION: Mass (nucleon) number - ANSWER-Sum of protons and neutrons in a nucleus.

,QUESTION: Electronic Configuration - ANSWER-Arrangement of electrons in an atom.




Shows principal quantum shells, sub-shells and number of electrons.




QUESTION: Number of electrons in each principal quantum shell - ANSWER-1: 2 electrons

2: 8 electrons

3: 18 electrons

4: 32 electrons




QUESTION: First ionisation energy (IE1) - ANSWER-The energy needed to remove 1 mole of electrons
from 1 mole of an element in the gaseous state to form 1 mole of gaseous ions.




QUESTION: Successive ionisation energies - ANSWER-The energy required to remove the first electron,
then the second, then the third, etc, from a gaseous atom.




1st ionisation energy: Li(g) —> Li+(g) + e-

2nd ionisation energy: Li+(g) —> Li2+(g) + e-

3rd ionisation energy: Li2+(g) —> Li3+(g) + e-




QUESTION: Factors that influence ionisation energy - ANSWER-The size of the nuclear charge

, Distance of outer electrons from the nucleus




Shielding effect of inner electrons




Spin-pair repulsion




QUESTION: Shielding - ANSWER-The ability of inner shell electrons to reduce the effect of the nuclear
charge on outer shell electrons.




QUESTION: Sub shells (subsidiary quantum shells) - ANSWER-Regions of principal quantum shells where
electrons exist in defined areas associated with particular amounts of energy. They are named s, p, d
,etc.




QUESTION: Atomic orbitals - ANSWER-Regions of space outside the nucleus that can be occupied by a
maximum of 2 electrons.




Orbitals are named s, p, d and f.




They have different shapes




QUESTION: Number of orbitals in each sub-shell - ANSWER-s - 1