Unit 1 : Topic 2 Flashcards
Atomic Structure and the Periodic Table
Chlorine has two possible isotopes, Cl³⁵ with a 75% abundance and Cl³⁷ with a 25% abundance. Predict the mass spectrum for the diatomic molecule.
Possible combinations of Cl₂⁺:
35+35 = 70
35+37 = 72
37+37 = 74
The 70:72:74 ratio is 9:6:1. Some fragmentation also causes peaks at m/z 35 and 37.
What does the first ionisation energy of successive elements provide evidence for?
Electron subshells.
Why does first ionisation energy drop between nitrogen and oxygen?
The electron removed from oxygen is part of an electron pair, so repulsion makes it easier to remove.
What rules do electrons follow when filling orbitals?
Electrons fill the lowest energy orbital first and prefer to occupy orbitals alone before pairing if possible.
Which two elements are exceptions to the rule that the 4s orbital is filled before the 3d orbital?
Chromium ([Ar]4s¹3d⁵) and copper ([Ar]4s¹3d¹⁰) due to increased stability.
Ions in a mass spectrometer can have a 2+ charge. True or False?
True. Ions in a mass spectrometer can have a 2+ charge, though a 1+ charge is more common.
What is first ionisation energy?
The energy required to remove one electron from one mole of gaseous atoms to form one mole of gaseous ions.
What do s and p orbitals look like?
The s-orbital is spherical, and the p-orbital is dumbbell-shaped.
Where is the mass of the atom concentrated?
In the nucleus.
What is the electron configuration of calcium?
Calcium has 20 electrons. Its configuration is [Ar]4s².
Use the graph to calculate the relative atomic mass of this substance.
[(79.2 × 17) + (80.1 × 83)] ÷ 100 = 79.95 g mol⁻¹.
What are the three subatomic particles in an atom?
Protons, neutrons, and electrons.
What is second ionisation energy?
The energy required to remove one electron from one mole of gaseous 1⁺ ions to form one mole of gaseous 2⁺ ions.
Why do atoms contain equal numbers of protons and electrons?
Atoms have a stable overall charge of 0. Protons are positively charged, and electrons are negatively charged, so they must balance.
What is a periodic property?
Recurring trends in physical and chemical characteristics across a period.
How does the atomic number and mass number differ between isotopes of the same element?
The atomic number remains the same as the number of protons is constant. The mass number differs due to variations in the number of neutrons.
Why does first ionisation energy drop between magnesium and aluminium?
The electron removed from aluminium is in the 3p orbital, which is higher in energy and further from the nucleus, reducing attraction.
What is a subshell?
A division of electron shells separated by orbitals, named s, p, d, and f.
Why does first ionisation energy increase across a period?
Nuclear charge increases, atomic radius decreases, and shielding remains constant.
Sodium has the atomic number 11 and mass number 23. How many protons, electrons, and neutrons does the Na+ ion have?
11 protons, 10 electrons, and 12 neutrons.
What factors influence ionisation energy?
The number of protons in the nucleus, the subshell from which the electron is removed, and electron shielding.
Boron has the atomic number 5 and mass number 11. How many protons, electrons, and neutrons does boron have?
5 protons, 5 electrons, and 6 neutrons.
What is the mass number?
The combined total of the number of protons and neutrons in an atom of an element.
What is an orbital?
The space where up to two electrons with opposite spins are likely to be found.
