Atomic Structure Flashcards
Atomic structure of an atom (3)
Mostly empty space
Very dense Nucleus made of protons and neutrneutrons
Electrons in energy shells
Mass of electron
1/1840
Proton number
Number of protons in the nucleus of an atom
Behaviour of subatomic particles in an electric field
Protons deflected to negative
Electrons deflected (more because they’re lighter) to positive
Atomic radius
Half the distance between the nuclei of 2 covalently bonded atoms (just measuring 1 will give you a different reading)
-only for neutral atoms
-cannot determine atomic radius of noble gases
-measured in nanometres x10^-9
Trends in atomic radius down a group
Atomic radius increases due to an increase in the number of energy shells and the shielding effect
Trends in atomic radius across the period (2)
-Atomic radius decreases across a period due to an increase in the number of protons resulting in a greater nuclear attraction between the electrons and the nucleus
-All atoms in the same period experience similar shielding
Ionic radius rule
The more positive the ion the smaller the atomic radius
The more negative the ion the larger the ionic radius
Graph to show the trend in ionic radius of successive elements in a period
Isotopes
Atoms having the same number of protons but a different number of neutrons
-have the same reactivity as they have the same no. Of valence electrons
-physical properties like mass + density change due to neutron no. Change
Relative isotopic mass
Relative mass of a single isotope compared with an isotope of carbon-12 which is assigned a relative mass of 12
Important rounding rules for Relative Atomic Mass and isotopic mass
RAM : 1dp
Isotopic mass : always a whole number
Rules for orbital diagrams (2)
Pauli’s exclusion principle - each orbital may contain a maximum of 2 electrons spinning oppositely
Hound’s rule - orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron
Free radical
Species with 1 or more unpaired electron
Ionisation energy
Energy required to remove the outermost electron from each atom in one mole of gaseous atoms to form one mole of gaseous ions with a charge of +1
Trends/factors that affect ionisation energy (3)
Distance from nucleus + shielding
Nuclear charge
Spin-pair repulsion
How distance from nucleus + shielding affects IE
As you move down a group, valence electrons are further from the nucleus and experience more shielding, reducing the force of nuclear attraction resulting in a lower ionisation energy
group with the highest ionisation energy
Group 8
How nuclear charge affects IE
Proton number increases as you move across a period, resulting in an increase in nuclear charge and a stronger nuclear attraction. ?The elements experience similar shielding, resulting in an increase in ionisation energy?
How spin-pair repulsion affects IE
Spin pair repulsion results in a lower ionisation energy as the paired electrons repel each other
Describe electron configuration
Electrons occupy orbitals that are found within energy shells
How are energy shells named
By quantum number (starting closest to the nucleus (1))
Orbitals
Areas within energy shells where electrons are found
S, p, d and f
Sub-shell
one or more orbitals in the same shell which have the same energy levels
Orbital rule
Each orbital can only hold 2 electrons
S-orbital
Only 1
Spherical in shape
Holds 2 total electrons
P-orbitals
3 - x y and z (each hold 2)
6 total electrons in P-subshell
Dumbbell shaped
D-orbitals
5 d-orbitals in d-subshell
Holds 10 electrons in total
Full electron configuration
Rules (2)
Big numbers never change
Fill 4s before 3d (3d has higher energy) and 5s before 4d
Why are there electron configuration exceptions
A half filled or full d-orbital is more stable than a partially filled one. (Stability is the goal)
Electron configuration exceptions (2)
Describe formation of ions (removing electrons)
The electrons are always removed from the shell furthest from the nucleus
How are energy levels numbered
According to their distance from the nucleus (lowest energy, n=1, closest to the nucleus
General ionisation energy equation
Representing electron configuration diagram (Aufbau)
+ rule
Always put one electron in each p orbital before pairing them
What type of reaction is ionisation energy
Endothermic
Relative atomic mass
Average mass of one atom of an element relative to the mass of one carbon-12 atom to which a value of 12 units is assigned
