Atomic structure and the periodic table

Question 1

What is relative atomic mass and formula

Answer 1

The mass of an element compared to 1/12 mass of a C12 atom

Ar =( average mass of atom of element / mass of one atom of c12 )
x 12

Question 2

What do relative isotopic mass and relative molecular mass use instead

Answer 2

relative isotopic mass uses mass of isotope and relative molecular mass uses mass of molecule

Question 3

As the distance from the nucleus increases how does this affect energy

Answer 3

Higher energy of shells

Question 4

What is Heinsberg’s uncertainty principle

Answer 4

You cannot say exactly where an electron is if you know its speed

Question 5

State Aufbau’s principle

Answer 5

electrons enter the lowest energy level first before filling the rest

Question 6

What is pauli’s exclusion principle

Answer 6

No two electrons can have the same 4 quantum numbers ( describe the movement and trajectory of an electron in an atom)

Question 7

what is Hund’s rule of maximum multiplicity ?

Answer 7

When two or more orbitals of equal energy (or very close energy) are available, electrons will fill the orbitals singly before filling doubly.

Question 8

What is the max number of electrons each shell can hold

Answer 8

2n^2 where n = the number of energy levels

Question 9

What is an atomic orbital

Answer 9

region around a nucleus which can hold up to two electrons with opposite spins

Question 10

What is an electron ?

Answer 10

Cloud of negative charge

Question 11

What are the 4 orbitals

Answer 11

• s orbital, spherical shape. Each shell has a single s orbital
• p orbital. dungbell shape. each shell except for first shell has 3p orbitals
• d orbital. various shapes. each shell except first and second have 5d orbitals
  f orbital. 7 different f orbitals found in shell 4 and above

Question 12

What are the three rules for filling atomic orbitals

Answer 12

• orbitals with lowest energy are filled first
• up to two electrons in each orbital if they have opposite spins
• if you have orbitals with same/ close energy you put electrons in individual orbitals first before doubling up

Question 13

What is the config for copper

Answer 13

1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^1

Question 14

What is the electronic config for chromium

Answer 14

1s^2 2s^2 2p^6 3s^2 3p^6 3d^ 5 4s^1

Question 15

Explain the electronic configuration exceptions for chromium and copper

Answer 15

3d sub shell is more stable when completely full or partially full
for Cr if there is only one electron in 4s subshell as opposed to two can have a half full 3d subshell
for Cu by having 1 electron in 4s subshell, can have a completely full 3d subshell

Question 15

What do groups 1 and 2 of periodic table correspond to

Answer 15

s1 and s2 subshells

Question 15

What does the transition block of metals correspond to

Answer 15

d1- d10 subshells

Question 16

What does group 3- 8 of the periodic table correspond to

Answer 16

p1 - p6 subshells

Question 17

Why are electrons in 4s always lost before 3d ones ?

Answer 17

4s subshell has a lower energy

Question 18

What is first ionisation energy ?

Answer 18

energy needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1 + ions

Question 19

What is second ionisation energy ?

Answer 19

energy needed to remove one mole of electrons from one mole of gaseous ions to form one mole of gaseous 2 + ions

Question 20

What are the three factors which affect ionisation energy ?

Answer 20

number of protons, atomic radius and shielding

Question 21

What does shielding refer to ?

Answer 21

electrons in the outer shell are repelled by electrons in the inner shells, so as number of inner shells increases attraction between nucleus and outer shell electrons decreases.

Question 22

How does number of protons affect ionisation energy ?

Answer 22

electrons are attracted to protons in the nucleus due to opposite charges attracting, so the greater the proton number, the greater the force of attraction between outer shell electrons and nucleus.

This would increase the ionisation energy

Question 23

How does first ionisation energy vary as you go down a group ?

Answer 23

• decreases as you go down group because the atomic radius increases due to more shells and also more shielding also due to greater shell number. Yes the number of protons increases but this is outweighed by the shielding and more shells. Of

Question 24

How does first ionisation energy vary accross a period ?

Answer 24

generally increases as you go accross a period. This is due to increasing proton number, which causes electrons to be pulled closer to nucleus, therefore decreasing size of atom ( atomic radius).Because of the same number of shells, shielding effect is the same/ similar.

Question 25

What are the exceptions to the general increase in ionisation energy across a period ?

Answer 25

from Be to Boron in group 2 there is a drop in ionisation energy. In boron outer electron removed is in a different subshell,2p which has higher energy than 2s subshell ( meaning it is further from the nucleus) so takes less energy to remove outer electron from boron than beryllium- less attraction between p subshell and nucleus.

from N to O another drop in ionisation energy, because in nitrogen each electron is in a separate 2p orbitals while in oxygen one of the orbitals contains an electron pair. An electron in a doubly occupied electron orbital is removed more easily due to repulsion between the two electrons, this requires less energy to remove.

*the 2p sub shell holds up to 6 electrons in 3 orbitals. In nitrogen the 2p sub shell has 1 electron in each orbital. In oxygen, the extra electron has to share an orbital.

Question 26

What is the use of a mass spectrometer?

Answer 26

To determine the mass number and abundance of isotopes of an element

Question 27

What is the electron impact method ?

Answer 27

• firstly substance must be vaporised
• high energy electrons knock electrons off atoms to form 1 + ions

Question 28

electron impact method is used for what kinds of compounds

Answer 28

Low MR compounds

Question 29

What is the electrospray method ?

Answer 29

• Sample is dissolved in a volatile solvent
• then sample injected through a hypodermic needle which turns sample into a mist
• very high voltage applied to needle tip which causes the sample to become protonated ( gains h + ions) sample becomes ionised

Question 30

How does a mass spectrometer actually work

Answer 30

Stage 1: Ionization: The atom is ionised by knocking one or more electrons off to give a positive ion. This is true even for things which you would normally expect to form negative ions (chlorine, for example) or never form ions at all (argon, for example). Mass spectrometers always work with positive ions.

Stage 2: Acceleration:The ions are accelerated so that they all have the same kinetic energy.

Stage 3: Deflection:The ions are then deflected by a magnetic field according to their masses. The lighter they are, the more they are deflected. The amount of deflection also depends on the number of positive charges on the ion - in other words, on how many electrons were knocked off in the first stage. The more the ion is charged, the more it gets deflected.

Stage 4: Detection: The beam of ions passing through the machine is detected electrically. When ions reach detector pick up an electron, flow of electrons causes an electric current. Electric current generates a mass spectrometer.

Question 31

How does the mass spectrometer figure out mass of isotope

Answer 31

• tine taken to move down drift chamber ( flight tube) used to figure out mass of isotope
• lighter ions travel fastest

Question 32

How does current produced relate to abundance of isotope ?

Answer 32

• size of current produced used to work out abundance of isotope
  more abundant isotope will produce a greater current

Question 33

What happens as the charge on an ion increases

Answer 33

time taken for it to reach detector decreases

Question 34

Why is the interior of the spectrometer a vacuum

Answer 34

So that the ions don’t collide with the air molecules

Question 35

What does the number of peaks tell you on a mass spectrum

Answer 35

the number of isotopes of an element, the higher the peak the greater the abundance of isotope

Question 36

What is relative isotopic mass

Answer 36

mass of an atom of an isotope compared with 1/12 mass of C12

Question 37

What is m/z ratio ?

Answer 37

• ratio of mass to charge of isotopes
• usually, ions just have a 1+ charge though so it can basically be considered the mass