Topic 2: Atomic structure Flashcards
Where are neutrons and protons located?
In the nucleus
Where are electrons located?
In the electron cloud surrounding the nucleus
Mass of electrons, protons, and neutrons (amu)
1/1840, 1, 1
(A/Z)X meaning
A= mass number
Z= atomic number
X=element symbol
Isotopes
Elements that have the same number of protons but a different number of neutrons
Chemical and physical properties of isotopes are…
Chemical properties are the same but physical properties are different
Examples of physical properties
Appearance, melting point, boiling point, density, solubility and texture
How are isotopes written?
With the mass number and elements symbol only (eg: Cl-35)
Relative atomic mass (Ar)
The average mass of an atom of the element, taking into account all its isotopes and their relative abundance
What does a mass spectrometer do?
It determines the relative atomic mass of an element from its isotopic composition
Why do isotopes have different physical properties?
They have different number of neutrons, meaning they have different densities
Why do isotopes have the same chemical properties?
Because isotopes have the same number of electrons, which means they take part in the same chemical reactions
Relationship between deflection and charge to mass ratio
The amount of deflection is proportional to the charge to mass ratio (m/z)
Relative abundance
The percentage of that isotope that occurs in nature
According to the Bohr model, electrons exist in
Energy levels
Atomic orbital
represents a region of space where there is a high probability of finding an electron
How to calculate relative atomic mass (Ar)?
The sum of the isotopic masses multiplied by their percentage abundances are added together and then divided by 100
The Bohr model
According to this model, electrons can only occupy certain energy levels within the atom and can transition between these energy levels by absorbing or emitting exact amounts of energy.
Main energy levels
numbers (1,2,3,4)
Sub-levels
s/p/d/f
s atomic orbital shape
Sphere
p atomic orbital shape
Dumbbell
How many orbitals in p sub-level?
3 (px,py,pz)–all at right angles to each other
Pauli exclusion principle says..
An atomic orbital can hold a maximum of 2 electrons and only if they have opposite spins
If energy level is n, what is the number of sub-levels and electrons per energy level?
n and 2n^2
The Aufbau principle
electrons fill atomic orbitals of lowest energy first
Write the condensed electron configuration of bromine (Z = 35)
[Ar] 4s2 3d10 4p5
What are the two exceptions to the Aufbau principle?
Chromium (Cr) and Copper (Cu)
Write the full electron configurations of Copper and chromium
Copper: 1s2 2s2 2p6 3s2 3p6 4s1 3d10
Chromium: 1s2 2s2 2p6 3s2 3p6 4s1 3d5
Write the electron configuration for the Ca2+ ion
1s2 2s2 2p6 3s2 3p6
State the electron configuration of a vanadium atom (Z = 23) and the vanadium(II) ion (V2+).
Atom: 1s2 2s2 2p6 3s2 3p6 4s2 3d3
Ion: 1s2 2s2 2p6 3s2 3p6 3d3
Hund’s rule
electrons fill orbitals in the same sub-level singly, before pairing up
Why are line spectra also called ‘rainbow barcodes’?
Different elements have different characteristic line spectra and can be used to identify elements.
Electromagnetic radiation: what is it and how can it be classified?
A type of energy that is all around us and takes many forms, such as radio waves, microwaves, X-rays and gamma-rays. Different types of EM radiation can be classified according to their energy, wavelength or frequency.
Wavelength
Wavelength (λ) is the distance between two crests in an oscillating wave. It has units of distance (m).
frequency
The frequency (v) is the number of waves that pass a point in one second. It has the units hertz (Hz) or s-1
Energy
Energy (E) of electromagnetic radiation depends on its frequency: a higher frequency means higher energy and vice versa. It has units of joules (J).
The equation of energy, wavelength and frequency of electromagnetic radiation
What does that say about their relationship?
c = vλ
- frequency and wavelength have an inverse relationship
- energy and wavelength have an inverse relationship
- frequency and energy have a direct relationship
The relative wavelength, frequency and energy of the infrared (IR) region, the visible region and the ultraviolet (UV) region.
IR: low energy, low frequency, long wavelength
Visible: medium energy, medium frequency, medium wavelength
UV: high energy, high frequency, short wavelength
What characterizes a continuous spectrum?
A continuous spectrum shows all the wavelengths or frequencies of visible light
What characterizes an absorption spectrum?
Some wavelengths of visible light are missing, shown by black lines on coloured background
What characterizes an emission light spectrum?
Coloured lines on a black background
How are absorption line spectra created? Give an example
When electrons absorb energy and transition from lower to higher energy levels.
(eg: transition from n=2 to n=3 absorb energy that correspond to the wavelength of red light, transition from n=2 to n=5 absorb energy that correspond to the wavelength of blue light)
At the high-energy (left) end of the spectrum, the lines…
converge
How are emission line spectra created? Give an example
When electrons emit energy and transition from higher to lower energy levels.
(eg: transition from n=3 to n=2 emit energy that correspond to red light, transition from n=5 to n=2 emits energy that correspond to the wavelength of blue light)
Equation that shows the relationship between energy and frequency
E=hv
where E is energy (in J), h is Planck’s constant (6.63 × 10-34 J s) and v is the frequency (in s-1)
Why is the hydrogen emission spectrum in particular studied in detail?
It is the simplest emission spectrum because it is only looking at the transition of one electron per atom
Electron transitions to the n = 1 energy level emit energy that corresponds to the wavelength or frequency of…
ultraviolet (UV) radiation
Electron transitions to the n = 2 energy level emit energy that corresponds to the wavelength or frequency of…
Visible light
Electron transitions to the n = 3 energy level emit energy that corresponds to the wavelength or frequency of…
Infrared (IR) radiation
