1: Atomic Structure and the Periodic Table Flashcards
What is the atomic number?
Number of protons
What is the mass number?
Number of protons and neutrons
What is the relative mass of each particle?
Proton - 1
Neutron - 1
Electron- 0.0005
What is an isotope?
Atoms of the same element with different numbers of neutrons
What are the properties of isotopes?
Same chemical properties (same electrons)
Slightly different physical properties (mass of atom)
What is the relative atomic mass (Ar)?
Weighted mean mass of an atom of an element, compared to 1/12 of the mass of an atom of Carbon-12
Average of the relative isotopic masses
What is the relative isotopic mass?
Mass of an atom of an isotope compared to 1/12 of the mass of an atom of Carbon-12
Usually a whole number
What is the relative molecular mass?
Average mass of molecule compared to 1/12 of the mass of an atom of the carbon-12
What is the calculation for the relative atomic mass?
Multiply each isotopic mass by % abundance, add them up
Then divide by 100
What are mass spectrometers?
Devices which find out what samples are made up of by measuring the masses of their components
What do mass spectrometers produce?
Mass spectra
What is on the y-axis of a mass spectra?
Abundance of ions (percentage)
Height of peak gives relative isotopic abundance
What is on the x-axis of a mass spectra?
m/z
Mass/charge ratio, most charges are +1 so usually just relative isotopic masses
How would you work out the relative atomic mass using a mass spectra?
Multiply relative isotopic mass by abundance and add up results
Divide by sum of the isotopic abundances
What are the 4 stages of mass spectroscopy?
Ionisation
Acceleration
Deflection
Detection
What happens in the ionisation stage of mass spectroscopy?
Sample bombarded with high energy electrons (causes one electron removed from each atom of sample)
What happens in the acceleration stage of mass spectroscopy?
All particles in sample accelerated to same kinetic energy
What happens in the deflection stage of mass spectroscopy?
Electromagnet creates magnetic field which deflects ions different amounts based on their m/z
Smaller the m/z, the larger the deflection
What happens in the detection stage of mass spectroscopy?
Ions hit detector which creates a current
The current is detected, amplified and recorded
What fields is mass spectroscopy used?
Radioactive dating
Space research
Sport to detect illegal drugs
Pharmaceutical industry
How would you calculate the isotopic mass from relative atomic mass and 2/3 isotopic masses?
Work out % abundance of unknown
Using Ar of element and the other two isotopes work out mass of isotope
What is the M peak?
Molecular ion peak - peak with highest m/z vlaue
Occurs due to formation of the molecular ion from the ionisation process
What are the first 4 energy subshells?
s
p
d
f
What is an orbital?
Bit of space that electrons move in
Electrons in the subshell have the same energy
What can be held in each orbital?
2 electrons
What happens to the 2 electrons in an orbital?
Spin-pairing
Electron spin in opposite directions
How many orbitals are found in the s sub-level?
1 orbital - 2 electrons
How many orbitals are found in the p sub-level?
3 orbitals - 6 electrons
How many orbitals are found in the d sub-level?
5 orbitals - 10 electrons
How many orbitals are found in the f sub-level?
7 orbitals - 14 electrons
What is the first ionisation energy?
Energy required to remove 1 mole of electrons from 1 mole of atoms of a gaseous element to form gaseous ions
What is the example equation for the first ionisation energy?
X (g) -> X+ (g) + electron
What is the example equation for the second ionisation energy?
X+ (g) -> X2+ (g) + electron
What factors affect ionisation energy?
Distance from nucleus
Nuclear charge (no. of protons)
Shielding
Why does 1st ionisation energy decrease as you go down groups?
Effective nuclear charge doesn’t change
Distance from nucleus increases
Shielding increases
Why does 1st ionisation energy increase as you go across periods?
Effective nuclear charge doesn’t change
Distance from nucleus decreases a very small amount
Shielding
Why does ionisation energy drop from phosphorus to sulphur?
Phosphorus - 3 electrons in the outer sub-level fill up each orbitals
Sulphur - 4 electrons mean that two electrons are in one orbital, they repel each other and therefore less energy required
What is the exception with subshell notation?
4s subshell has a lower energy level than the 3d subshell
4s fills up first
What is the electronic configuration of chromium?
1s2 2s2 2p6 3s2 3p6 3d5 4s1
What is the electronic configuration of copper?
1s2 2s2 2p6 3s2 3p6 3d10 4s1
What is the electromagnetic spectrum?
Energy that is transmitted as waves with a spectrum of frequencies
What are electron shells also known as?
Quantum cells
Energy levels
What is excitation?
Electrons take in the energy from their surroundings and move to a higher energy level
What happens in de-excitation?
Electrons release specific amounts of energy and drop to a lower energy level
Produces a specific frequency of light
How can the emission spectra be displayed?
Line spectra of discrete coloured lines
Each spectrum for each element is different
What are the four basic principles of quantum shells?
Only exists in fixed orbits
Fixes energy
When electrons move between orbits EM radiation is emitted or absorbed
Radiation will have a fixed frequency
Why is the 1st ionisation energy of O less than N?
The extra electron of oxygen will cause it to go into an orbital with another electron (2p4) Nitrogen is (2p3), therefore only one electron in each orbital
What is constant with elements in the same period?
Same number of electron shells
What is constant with elements in the same group?
Same number of electrons in their outer shell (similar chemical properties)
What is periodicity?
Repeating pattern in physical (and other) properties across period 2 & 3
How does atomic radius change across a period?
Decreases - as protons increases so the positive charge increases and electrons are pulled closer
What is the s-block?
Group 1 and 2, outer electron always in s-orbital
Easily loses electron
What is the d-block?
Most transition metals in the central block, outer electron in d-orbital
What is the p-block?
Groups 3-0, outer electron in p-orbital
How does boiling point change across period 2 and 3?
Generally increases to group 4 then decreases to 8
What elements in group 2 has the highest and lowest boiling temperature?
Highest - Carbon (Group 4)
Lowest - Neon (Group 8 )
Explain the trend of melting/boiling points across a period
Group 1-3 have metallic bonding, increasing in strength due to increased charge density
Group 4 has giant covalent lattice and strong covalent bonds
Groups 6-7 simple molecular structures
Group 8 noble gases
Why do noble gases have low boiling points?
Exist as individual atoms and therefore have very weak London forces
Why does Sulphur have an unusually high boiling/melting point?
Naturally occurs as S8
Larger London forces as more electrons
What block of the periodic table is chromium found?
d
1s2 2s2 2p6 3p6 4s2 3d4
What will have the highest to lowest ionisation of the following species:
S S+ S-
Highest: S+
S
Lowest: S-
What would be the groups of the elements (with consecutive atomic numbers) with the following ionisation energies:
1680, 2080, 496, 738
7, 8, 1, 2
Why do increasing numbers of protons not have a large effect if there are also more electrons?
Extra shells and electrons meaning the force is spread more and therefore effectively the same
