Chapter 4- Structure Flashcards
What is meant by the term ‘isotope’?
Isotopes are atoms of an element that have the same number of protons and electrons but different numbers of neutrons
Which sub-atomic particles are present in the nuclei of atoms?
Positively charged protons and neutral neutrons. Both have a relative mass of 1
In a neutral atom, what’s the ratio of electrons to protons?
1:1. This is because electrons have a relative charge of -1 and protons are +1
Why is the chemistry of an atom not affected by being an isotope?
They don’t have a charge, so don’t affect how protons and electrons interact
What does change between isotopes?
Physical properties, like mass, and melting and boiling points
How does alpha decay convert one atom to another?
A helium nucleus is released, reducing the mass number by 4 and atomic number by 2. The new atom has a charge of 2-.
How does beta decay convert one atom to another?
A neutron turns into a proton, and an electron leaves the atom. The mass number stays the same but the atomic number increases by 1. The charge is 1+
Energy=
frequency x Planck’s constant (6.626*10^-34)
Speed of light (2.998*10^8)=
frequency x wavelength
How is E=hv combined with c=vλ?
v=c/λ
∴ E=hc/λ
How is the energy of a photon converted into energy per mole?
Times by Avogadro’s constant (6.022*10^23)
What are the four quantum numbers that can be assigned to electrons?
Principal QN, azimuthal QN, magnetic QN, spin QN
What does the principle quantum number (n) represent?
The energy level
What values can the principle quantum number take?
1, 2, 3, …, ∞
What does the azimuthal quantum number (ℓ) represent?
The angular momentum of an atomic orbital (orbital type)
What values can the azimuthal quantum number take?
0, 1, 2, …, (n-1)
What does the magnetic quantum number (ml) represent?
The orientation of orbital in space (the specific orbital)
What values can the magnetic quantum number take?
-ℓ to +ℓ, inclusive of zero
What does the spin quantum number (ms) represent?
Which way the electron is spinning
What values can the spin quantum number take?
±0.5
State the aufbau principle
The aufbau principle states that in the ground state of an atom/ion, electrons fill atomic orbitals of the lowest available energy levels before filling higher levels
What is the Pauli exclusion principle?
Electrons in the same atom can’t have the exact same four quantum numbers
State Hund’s first rule
Every orbital in a sublevel is singly occupied before any orbital is doubly occupied. All of the electrons in singly occupied orbitals have the same spin (to maximize total spin).
What do boundary surface diagrams represent?
Boundary surface diagrams are a good representation of shapes of atomic orbitals. Boundary surface diagrams are considered an acceptable approximation of shape of orbital if the boundary surface encloses the region with probability density of more than 90%.
What are some of the features of boundary surface diagrams?
1) Shape of the surface diagram: It changes depending on the azimuthal quantum number
2) Size of the surface diagram: The boundary surface diagram of an orbital increases in size as principle quantum number increases
3) Nodes in the surface diagram: Nodes are the region where the probability density goes to zero. There are (n-1) nodes in the boundary surface diagram of all orbitals
Why do boundary surface diagrams never have a probability density of 100%?
At any distance from the nucleus, the probability of finding an electron is never zero. It will always have some finite value, so it’s not possible to draw a boundary surface diagram which encloses the region with 100% probability density
Describe what is meant by electron shielding
The shielding effect describes the attraction between an electron and the nucleus in any atom with more than one electron shell. It can be defined as a reduction in the effective nuclear charge on the electron cloud, due to a difference in the attraction forces of the electrons on the nucleus
What’s the difference between valence and core electrons?
Valence electrons may participate in chemical reactions, while core electrons do not. This is because valence electrons are accessible, and core electrons are inaccessible
Describe an ambiguity of valence and core electrons for elements in the d and f blocks
The nearly equal energies of ns and (n - 1)d orbitals. The definitions of core and valence electrons do not depend on whether the electrons are used in chemical reactions, but rather whether they are in an accessible energy level or not.
What is the shape of s orbitals?
Spherical
What is the shape of p orbitals?
Dumbbell shaped, aligned on either the x, y, or z axis
What is the shape of the d orbitals?
Four of the d orbitals are butterfly shaped, and one has an unusual shape that looks like a doughnut surrounding a Q-tip
Define the term ‘node’
Nodes are the points in space around a nucleus where the probability of finding an electron is zero.
What are the two types of node?
Radial nodes and angular nodes.
What are radial nodes?
A radial node occurs when the radial wavefunction is equal to zero, which occur inside the orbital lobes
What are angular nodes?
An angular node is a region where the angular wavefunction is zero. In the case of the p-orbitals, this is a plane, although angular nodes are not necessarily planes.
How do you work out the number and type of nodes for an orbital?
Number of nodes= n - 1
Angular nodes= ℓ
Radial nodes= (number of nodes) - (angular nodes)
How many nodes exist in the first shell?
For the first shell, n=1, which means the number of nodes will be 0.
How many nodes exist in the second shell?
For the second shell, n=2, which yields 1 node. 2s orbital: ℓ=0, which means the node will be radial. 2p orbital: ℓ=1, which means the node will be angular
How many nodes exist in the third shell?
The third shell, n=3, yielding 2 nodes. 3s orbital: ℓ=0 meaning no angular nodes, and thus the two nodes must be radial. 3p orbital: one angular node, meaning there will be one radial node as well. 3d orbital: two angular nodes, and therefore no radial nodes
