Atomic Orbitals, Electronic Configurations and the Periodic Table Flashcards
How can the discrete lines observed in atomic spectra be explained?
If electrons, like photons, also display the properties of both particles and waves
How do electrons behave in an atom?
As standing waves. These are waves that vibrate in time but do not move in space.
What are the different sizes and shapes of standing wave around the nucleus known as?
Orbitals
How many electrons can orbitals hold?
A maximum of 2
What are the different shapes of orbitals?
s, p, d, f
Electrons within atoms have fixed amounts of energy called…
Quanta
What is the principal quantum number, n?
Indicates the main energy level for an electron
Higher n = bigger s orbital
What is the angular momentum quantum number, l?
Determines the shape of the subshell and can have values from 0 to (n − 1)
What is the magnetic quantum number, ml?
Determines the orientation of the orbital and can have values between −l and + l
What is the spin magnetic quantum number, ms?
Determines the direction of
spin and can have values of +1/2 or −1/2
What is the aufbau principle?
Electrons fill orbitals in order of increasing energy
What is Hund’s Rule?
When degenerate orbitals are available, electrons fill each singly, keeping their spins parallel before spin pairing starts (this is to maximise the number of parallel spins or increase spin multiplicity)
What is the Pauli Exclusion Principle?
No two electrons in one atom can have the same set of four quantum numbers, therefore, no orbital can hold more than two electrons and these two electrons must have opposite spins
In an isolated atom the orbitals within each subshell are…
Degenerate
What does it mean if an atom is in the s block of the periodic table?
It’s outermost electron is in an s orbital
What does it mean if an atom is in the p block of the periodic table?
It’s outermost electron is in a p orbital
What does it mean if an atom is in the d block of the periodic table?
It’s outermost electron is in a d orbital
What does it mean if an atom is in the f block of the periodic table?
It’s outermost electron is in a f orbital
Why does nitrogen have a higher ionisation energy that oxygen?
The electron is being removed from a half full p orbital in nitrogen, this is a stable electron arrangement
Why does boron have a lower ionisation energy than beryllium?
The electron being removed from beryllium is being removed from a full s orbital which is a stable electron arrangement
The electron being removed from boron is further away from the nucleus
How can the number of electron pairs surrounding a central atom be found?
• taking the total number of valence (outer) electrons on the central atom and adding one for each atom attached
• adding an electron for every negative charge
• removing an electron for every positive charge
• dividing the total number of electrons by two to give the number of electron pairs
Electron pairs are negatively charged and repel each other. They are arranged to…
Minimise repulsion and maximise separation
The arrangement of electron pairs around a central atom is…
• linear for two electron pairs
• trigonal planar for three electron pairs
• tetrahedral for four electron pairs
• trigonal bipyramidal for five electron pairs
• octahedral for six electron pairs
Electron pair repulsions decrease in strength in the order. What is meant by this?
non-bonding pair/non-bonding pair > non-bonding pair/bonding pair > bonding pair/bonding pair
