Atomic Structure

Question 1

Isotope Definition

Answer 1

are atoms with the same atomic number but different mass number
they have same number of electrons and so their chemical properties are similar but physical properties may differ

Question 2

Mass Spectrometer

Answer 2

is used to determine the relative atomic mass of an element from its isotopic composition
the atoms are deflected by a magnetic field
the lighter they are the more they are deflected
the more the ion is charged the more it gets deflected

Question 3

Why is C12 chosen as a standard?

Answer 3

• you can get it in pure form
• it doesn’t react with O2 or H2O in air
• solid
• plentiful

Question 4

Calculating Relative Atomic Masses

Answer 4

using %
add the sum of the (mass number x % composition) for all the isotopes and divide the total by 100

Question 5

Calculating abundance of isotopes

Answer 5

Equate one isotope to x% and the other to 10-x%
then create equation using same method as for relative atomic mass

Question 6

Frequency definition

Answer 6

the number of waves that pass a particular point per second
the shorter the wavelength the higher the frequency

Question 7

Continuous spectrum Definiton

Answer 7

shows an unbroken sequence of frequencies such as the spectrum of visible light

Question 8

Line Emission Spectrum Definition

Answer 8

has only certain frequencies of light as it is produced by excited atoms and ions as they fall back to a lower energy level (coloured bands)

Question 9

Line Absorption Spectrum Definition

Answer 9

is a continuous spectrum except for certain colours which are absorbed as the atoms are excited to higher energy levels (black bands)

Question 10

Ground State of an atom

Answer 10

the electrons occupy orbitals with the lowest possible energy

Question 11

What happens when an atom is excited?

Answer 11

occurs when an atom absorbs energy
the electrons gain energy and move further from the nucleus to a higher energy level
however, this excited state os unstable
so the electron eventually falls back to lower energy levels giving out electromagnetic waves (photon - discrete amount of energy)

Question 12

What does “energy levels are concentric and convergent” mean?

Answer 12

concentric means that they are within one another (like a target)
convergent means that they are getting closer together the further away from the nucleus

Question 13

Formulas to do with energy of photon released

Answer 13

energy of photon of light emitted = energy change in the atom
energy emitted = frequency of raditation given by Planck equation
Eelectron = hv

Question 14

The Emission Line Spectrum of Hydrogen

Answer 14

1. the lines converge as the energy levels increase
2. when electrons return to n=1 energy level, UV light is emitted
3. when electrons return to n=2 energy level, visible light is emitted
4. when electrons return to n=3 energy level, infrared light is emitted
   i.e. the smaller the drop the lower energy of the photon (lower frequency on EM spectrum)

Question 15

What does the limit of convergence indicate?

Answer 15

it indicates the energy required to completely remove the electron from the atom - ionisation energy

Question 16

What is the general formula for the maximum number of electrons in each main energy level?

Answer 16

2 x (n)^2

Question 17

What does ionisation energy provide evidence for?

Answer 17

• the number of electrons in each energy level
• the existence of sub-levels within energy levels
• the extra stability of filled and half filled p and d sublevels

Question 18

First Ionisation Energy Definition

Answer 18

the minimum amount of energy required to remove ONE MOLE of electrons from ONE MOLE of gaseous atoms to form ONE MOLE of gaseous ions

Question 19

Second Ionisation Energy

Answer 19

the energy required to remove a second mole of electrons from an ion

Question 20

What lowers the value of ionisation energy?

Answer 20

as electrons are negatively charged and the nucleus is +ve, there will be an attraction between them. The greater the pull of the nucleus the harder it will be to remove an electron

• filled inner shells exert a SHIELDING effect, and hence lowers the effective nuclear pull
• electrons FURTHER away from the nucleus = lower nuclear attraction for an electron

Question 21

Variation in 1st ionisation energy across a period

Answer 21

there is a general increase across a period before the value drops dramatically for the start of another period. This is because as you go across a period, the nuclear charge (number of protons) increases and therefore a greater attractive force for the outer electrons

Question 22

Variation in 1st ionisation energy down groups

Answer 22

GROUP 1 - the value decreases down the group despite an increased nuclear charge the electron is easier to remove due to an increased shielding and greater distance from the nucleus so the outer electron is held less strongly and is easier to remove
GROUP 2 - similar to group 1. Group 2 values are greater than their group 1 neighbours as the increased nuclear charge = stronger pull on electron and more energy required to remove an electron

Question 23

s sublevels

Answer 23

only have one orbital and therefore a maximum of 2 electrons
they are spherically shaped

Question 24

p sublevels

Answer 24

contain three orbitals and therefore contain a maximum of (3x2) = 6 electrons
they are dumb bell shape

Question 25

d sublevels

Answer 25

contain 5 orbitals and therefore contain a maximum of 10 electrons
they vary in shape

Question 26

f sublevels

Answer 26

contain 7 orbitals and therefore a maximum of 14 electrons
they also vary in shape

Question 27

Order of filling energy sublevels and orbitals

Answer 27

always fill up the orbitals of lowest energy first
* the 4s orbital has an energy value between 3p and 3d so is filled before 3d
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 …

Question 28

Pauli’s Exclusion Principle

Answer 28

an orbital can only contain 0, 1 or 2 electrons

Question 29

Hund’s Rule

Answer 29

in an orbital electrons spin one of two ways
two electrons in the same orbital must spin in opposite directions in order to minimise repulsion

Question 30

Afbau Principle

Answer 30

electrons are placed in the lowest energy orbitals first, as it gives the most stable configuration called the ground state

Question 31

Cr electron arrangement

Answer 31

1s2 2s2 2p6 3s2 3p6 3d5 4s1
* as it is more energetically favorable to have a half filled sub shell

Question 32

Cu electron arrangement

Answer 32

1s2 2s2 2p6 3s2 3p6 3d10 4s1
* more energetically favorable to have a filled d shell and half filled s shell

Question 33

Isoelectronic ions

Answer 33

means they all have the same electron configuration after electrons are added to the outermost p sub shell

Question 34

How can the frequency or wavelength of the radiation in the emission spectrum at the limit of convergence be used to determine the ionisation energy?

Answer 34

E = hv and c=vλ
as v=c/λ
E=hc/λ