1
Q
What is electron configuration
A
- Is the arrangement of electrons of an atom, a molecule
- Electron configuration concerns how electrons can be distributed in the orbital of a given system ( atomic or molecular )
2
Q
Explain the electronic structure of atoms
A
- 4 different quantum numbers describe each electron in an atom
- 3 of these quantum numbers ( n, l, and ml ) represent the 3 dimensions of space in which an electron could be found
- A wave function for an electron gives the probability of finding the electron at various points in space
- The wave function is called an atomic orbital
- The 4th quantum number (s or ms) refers to a certain magnetic quantity called spin.
3
Q
Why is it usefull to know the elctron configuration
A
- Useful in understanding the structure of the periodic table of elements
4
Q
Explain the principal quantum number
A
- ” n “
- Relates to the size of the atomic orbital.
n can have any positive integer value from 1 to ∞ - The smaller the n, the lower the energy, and the smaller the orbital; the higher the value of n, the higher the energy and the larger the orbital
- Orbitals of the same quantum state ( n ) belong to the same shell.
5
Q
Explain the angular or orbital quantum number
A
- ” l “
- Distinguishes orbitals of a given n value which have different states
- This number gives the shape of the orbital
- l can have any integer value from 0 to (n−1).
6
Q
Explain the magnetic quantum number
A
- ” ml “
- This 3rd number has to do with the orientation of the electron’s orbital or angular momentum in a magnetic field
- ml can take on integer values ranging from − l to + l
7
Q
Explain the spin quantum number
A
- ” s “ / “ ms “
- It describes the spin orientation of an electron: ms = +1/2 ( spin up: ↑) or ms = −1/2 (spin down ↓)
8
Q
Explain shells and subshells
A
- The electron configuration of an atom is the particular distribution of electrons among available shells
- An electron shell is the set of allowed states electrons may occupy that share the same n ( the number before the letter in the orbital label )
9
Q
Explain an atom’s nth electron shell
A
- Can accommodate 2n2 electrons, e.g. 1st shell ( n = 1: K shell): 2 electrons; 2nd shell ( n = 2: L shell ) : 8 electrons and 3rd shell (n=3: M shell ): 18 etc.
- The factor of 2 arises because the allowed state is double due to spin
10
Q
Explain subshells fully
A
- A subshell is the set of states defined by a common orbital quantum number, l, within a shell
- Electrons with the same values of n and l are referred to as being in the same subshell
- The values l = 0, 1, 2, 3, 4, 5,… Correspond to the s, p, d, f, g, h,… labels, respectively.
- The Pauli exclusion principle limits the maximum number of electrons in each subshell to 2 ( 2 l + 1)
- This gives 2 electrons in an s subshell, 6 in p, 10 in d, and 14 in f
11
Q
What is Pauli’s exclusion principle
A
States that no two electrons in the same atom can have the same values of the 4 quantum numbers
12
Q
What is Z
A
Atomic numbers of an element
13
Q
Explain Aufbau principle
A
- Was an important part of Bohr’s original concept of electron configuration
- A maximum of 2 electrons are put into orbitals in the order of increasing orbital energy
- The lowest-energy orbitals are filled before electrons are placed in higher-energy orbitals
- This principle works very well ( for the ground states of the atoms ) for the 1st 18 elements ( H to Ar ) then decreasingly well for the following 100 elements ( K to Fm )
- The modern form of the Aufbau principle is given by Madelung’s rule
14
Q
Explain Madelung’s rule
A
- Orbitals are filled in the order of increasing n+ l
- Where two orbitals have the same values of n+ l, they are filled in order of increasing n.
This gives the following order for filling the orbitals:
1s 2s 2p 3s 3p 4s 3d 4p 5s 6s 4f 5d 6p 7s 5f 6d 7p
15
Q
What are conduction electrons
A
- Let’s use a simple metal: Na (Z=11 )
- Consider Na gas = collection of free Na atoms with Z=11 electrons
- Electronic configuration: 1s2 2s2 2p6 3s1
- Valence electrons are responsible for most of the chemical properties of Na. In chemical reaction Na loses this valence e-, and Na+ is formed
Ex.: NaCl: valence e- of Na is transferred to the Cl atom
- Valence electron loosely bound to the rest. Occupies the 3rd atomic shell
- 10 core electrons which comprise the stable structure of the filled 1st and 2nd shells
16
Q
Explain electric charge
A
- There are 2 types of electric charges in nature:
- Positive change : H+ ( proton ), Cu2+
- Negative charge : e- ( electron ), SO42-
- The SI unit for charge is Coulomb (C)
- The magnitude of the fundamental charges are exactly equal: e = 1.602 × 10-19 C
17
Q
Explain force
A
- Unlike charges attract and like charges repel
- Magnitude of force is given by Coulomb’s Law
F = K qQ / r^2 k = 9 x 10^9
18
Q
What is a dielectric material
A
An electrically insulating and may be made to exhibit an electric dipole structure
i.e. separation of positive and negative charged entities on a molecular/atomic level
19
Q
Explain an electric dipole ( p )
A
- The interaction between p and E is the basis of capacitors
- A capacitor is a device that can maintain a potential difference, storing energy by storing charge
- A pair of conductors, whether separated by empty space or by an insulator material ( dielectric ) forms the simplest type of capacitor
20
Q
Explain a capacitor
A
- Electrical potential energy can be stored in it
- Consists of 2 parallel plates with equal but opposite charges; separated by a dielectric material
- The capacitance is related to the amount of charge that a capacitor can store per unit of voltage
c = Q / V
- 1 F is the amount of capacitance when 1 C of charge is stored with 1 V across the plates
21
Q
Explain batteries
A
- A battery is a chemical device for the storage of energy
- Whereas the potential of a capacitor decreases as the capacitor delivers its charge, a battery ideally maintains a fixed potential between two points (terminals) as it deliver charge
**Anode ( A ) and Cathode ( C ) are made of dissimilar conductor materials with different electrochemical potential
22
Q
Explain Electrochemical potential
A
- Measures the tendency to lose electrons ( opposite of the electronegativity but the scale is not the same )
- Electrolytes work as an insulator for electron flow.
- Electrons flow through the load in the external circuit
Example of the electrochemical Reactions : Consider zinc immersed in an acid solution containing H+ ions ; Zn will experience oxidation or corrosion
23
Q
Explain the make up of a battery
A
- Three parts: Anode (-); cathode (+) and electrolyte
- Reactions in the battery cause a build-up of electrons at the anode, causing the voltage
- The electrolyte keeps the electrons from going straight from the A to the C within the battery
- The electrochemical processes change the chemicals in A and C and eventually stop the supply of electrons i.e. there is a limited amount of power
24
Q
Explain charging fully
A
- Changes the direction of the flow of electrons using a power source
- The positive of the power source is connected to the cat where it will extract the electrons (making it (+)) and force them into the Anode (making it (-))
- This is an unstable condition ( when the battery is charged )
- The moment a load is connected between the Anode and the cathode, the electrons slide back to the cathode as from the top of the hill
- The porous separator ( permeable to ions and not electrons ) is there for security reasons to prevent a short circuit situation if the electrolyte gets depleted for instance when the internal temperature of the battery increases for some reason
