1 - Atomic structure and the periodic table Flashcards
What are isotopes?
Isotopes are atoms of the same element with the same number of protons and electrons but a different number of neutrons.
What are ions?
Ions are charged particles formed when atoms lose or gain electrons to gain stability.
What is relative isotopic mass?
The mass of an atom of an isotope of an element compared with 1/12th the mass of an atom of carbon-12.
What is relative atomic mass?
The weighted average mass of an atom of an element compared with 1/12th the mass of an atom of carbon 12.
What is a mass spectrometer used for?
It is an analytical piece of equipment. It is used to find the relative abundances of isotopes in a sample of an element.
What type of molecules can be read by a mass spectrometer?
Positive ions only.
what is a molecule?
2 or more atoms bonded together.
If a question asks you to identify the species responsible for a peak on a mass spectrum, you would write:
e.g 35Cl+
in mass spectroscopy, how are does a molecule become a positively charged ion?
The molecule is bombarded with electrons.
what is an atomic orbital?
a region of space around the nucleus that can hold up to 2 electrons with opposite spins.
Main features of the s-orbital
- each shell contains 1
- spherical in shape
- each s subshell holds 2 electrons
Main features of the p-orbital
- 3 in every shell from 2nd shell
- dumbbell shape
- each p subshell holds 6 electrons
d-orbital
- each shell from 3rd shell contains 5
- D orbitals can hold 10 electrons.
f-orbital
- each shell from 4th shell contains 7
- F subshells can hold 14 electrons
why is 4s filled before 3d?
Sub shells fill in order of increasing energy. 4s has less energy than 3d, so 4s is filled in first. However, when electrons are lost, they are lost from 4s first.
how are electron configurations drawn?
- 2 electrons of opposite spin in each orbital.
- each orbital gains 1 electron before the sub shell finishes filling up.
why are copper and chromium exceptions to the normal electron structure?
in both cases, is it a more stable arrangement to move 1 electron from the 4s sub shell to ‘fill out’ the 3d sub shell.
what do you need to remember about ions when writing electron configuration?
remember that 4s is part of the outermost shell so electrons are lost from there first (even though it was filled up first).
when writing electron configuration and electrons filled in 4s and 3d, what do you write first?
even though 4s fills in first, you write it in number order (e.g …3p6 3d9 4s2)
What is first ionisation energy?
First ionisation energy is the energy required to remove one electron from each atom in one mole of atoms of an element to form one mole of positive 1+ ions in the gaseous state.
what is second ionisation energy?
Second ionisation energy is the energy required to remove one electron from each 1+ ion in one mole of 1+ ions of an element to form one mole of 2+ ions in the gaseous state.
what are the factors that affect ionisation energy?
- attraction of the nucleus
- atomic radius (distance of outermost electrons from nucleus)
- shielding effect
explain the trend in first ionisation energy down a group.
- although nuclear charge increases
- atomic radius increases (distance between outermost shells and nucleus increases.)
- and electron shielding effect increases
- so the force of attraction between the outermost electrons and nucleus decreases.
- so first ionisation energy decreases.
explain the trend in first ionisation energy across a period.
- nuclear charge increases
- atomic radius decreases (number of shells stays the same, number of electrons and nuclear charge increases, force of attraction between them increases).
- shielding effect stays the same (same number of shells).
- force of attraction between nucleus and outermost electrons increases
- first ionisation energy increases.
