Ch2 Atoms and electrons

Question 1

Atomic number

Answer 1

number of protons in an atom of an element
e.g. proton number

Question 2

Mass number

Answer 2

no of protons + neutrons in the nucleus of an atom
e.g. nucleon number

Question 3

ion

Answer 3

An electrically charged particle formed by loss or gain of an electron

Question 4

relative charges of particles

Answer 4

p - +1
n- 0
e- -1

Question 5

relative mass of particles

Answer 5

p- 1
n- 1
e- 1/2000

Question 6

Isotopes

Answer 6

atoms of same element that have different masses. Has same number of electrons and protons, but different number of neutrons

Question 7

TOF mass spectrometer

Answer 7

1. Take a sample of the element(contains all different isotopes)
2. The atoms then go through ionisation and are converted into positive ions(bombarded with high-energy electrons, knocking off electrons from outer shell which can cause fragmentation)
3. The positive ions are now attracted to a negatively charged plate, increasing their kinetic energy and causing them to accelerate
4. All the ions with the same charge will have the same kinetic energy
5. The ions stop accelerating once they pass the negative plate and they drift down the chamber towards the detector at different velocities(lighter ions are faster)
6. The ions reach the detector and gains electrons. The time taken to reach the detector is used to determine the mass of the isotope
7. This flow of electrons causes a current to flow. The size of the current produced when each isotope hits the detector is used to determine the abundance of the type of isotope (more abundant= greater current)

Question 8

General mass spectrometer

Answer 8

1. Take a sample of the element(contains all different isotopes)
2. The atoms then go through ionisation and are converted into positive ions(bombarded with high-energy electrons, knocking off electrons from outer shell)
3. The positive ions are now attracted to a negatively charged plate, increasing their kinetic energy and causing them to accelerate
4. The ions stop accelerating once they pass the negative plate and they drift down the chamber towards the detector
5. The focused stream of ions pass through a magnetic field and constant speed and are deflected
6. The degree of the deflection depends on the mass of the ion, which the detector is calibrated to record and interpret

Question 9

why mass spectrometer has a pump

Answer 9

to create a vacuum to prevent ions colliding with molecules in the air

Question 10

Mass spectra readings

Answer 10

stick on m/z axis- presence of a positive ion formed by isotope
height of stick - abundance

Question 11

molecular ion peak

Answer 11

peak corresponding to relative molecular mass of compound

Question 12

fragmentation

Answer 12

after ionisation, molecular ions are energetically unstable and so bonds break to form smaller molecules

Question 13

Ground state

Answer 13

How the atoms naturally exists with its electrons in their lowest energy position(close as allowable to nucleus)

Question 14

Evidence for existence of electron shells

Answer 14

Ionisation energies- large noticeable jumps in energy shows electron is being removed from shell nearer to nucleus

Question 15

First ionisation energy

Answer 15

the energy required to remove one electron from each atom in one mol of gaseous atoms to form one mole of gaseous 1+ ions

Question 16

Evidence for existence of sub-shells

Answer 16

There are peaks and troughs in first ionisation energy of elements as they fill up a shell

Question 17

orbitals

Answer 17

region around the nucleus of an atom that can hold up to a maximum of two electrons(spin in different directions)

Question 18

Energy level order

Answer 18

1s,2s,2p,3s,3p,4s,3d,4p,5s,4d ect

Question 19

s orbital

Answer 19

spherical volume of negative charge with nucleus at centre
as pqn increases, radius at which charge is most dense becomes further away from nucleus

Question 20

p orbital

Answer 20

elongated dumbbell shape
variable charge density
3 p orbitals(x,y and z) per principal quantum number
area of greatest concentration increasing with distance from nucleus as pqn increases

Question 21

principal quantum number

Answer 21

numbers 1,2,3
divided into sub-shells

Question 22

sub-shell names

Answer 22

relate to appearance of lines in emission spectra(small bursts of energy when electrons jump from energy level)

s- sharp
p- principal
d- diffuse
f- fundamental