Atomic structure

Question 1

What is the mass and charge on a proton?

Answer 1

1 +1

Question 2

What is the mass and charge on an electron?

Answer 2

1/2000 -1

Question 3

What is the mass and charge on a neutron?

Answer 3

1 0

Question 4

What is the definition of an atom

Answer 4

Atom -the smallest particle of a chemical element that can exist.

Question 5

What is the definition of an Ion

Answer 5

Ion -an atom or molecule with a net electric charge due to the loss or gain of one or more electrons

Question 6

What is the definition of an Cation

Answer 6

Cation – a positively charged ion due to the loss of electron(s)

Question 7

What is the definition of an Anion

Answer 7

Anion – a negatively charged ion due to the gain of electron(s)

Question 8

What is the definition of an Isotope

Answer 8

Isotope – atoms of the same element that contain the same number of protons but a different number of neutrons.

Question 9

What is the definition of an Atomic number

Answer 9

Atomic number – the number of protons (or electrons) in an atom.

Question 10

What is the definition of an Mass number

Answer 10

Mass number – the total number of protons and neutrons in the nucleus of an atom.

Question 11

What is the definition of an Relative atomic mass

Answer 11

Relative atomic mass – the average mass of an atom of an element relative to 1/12 the mass of an atom of carbon-12.

Question 12

What is the definition of an Relative isotopic mass

Answer 12

Relative isotopic mass – the mass of a single isotope of an element relative to 1/12 the mass of an atom of carbon-12.

Question 13

What is the definition of an First ionisation energy

Answer 13

First ionisation energy – the energy needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions.

Question 14

What is electron impact in time of flight mass spec?

Answer 14

The Sample is vaporised and then high energy electrons are fired at it. The high energy electrons come from an ‘electron gun’ which is a hot wire filament with a current running through it that emits electrons. This usually knocks off one electron from each particle forming a 1+ ion.

Question 15

What is the equation for electron impact TOF?

Answer 15

M(g) + e- -> M+(g) + 2 e-

Question 16

What is electrospray ionisation in time of flight mass spec?

Answer 16

The The sample is dissolved in a volatile solvent and injected through a fine hypodermic needle to give a fine mist. The tip of the needle is attached to the positive terminal of a high-voltage power supply. The particles are ionised by gaining a proton (i.e. an H+ ion which is simply one proton) from the solvent as they leave the needle producing XH+ ions (ions with a single positive charge and a mass of Mr + 1).

Question 17

What is the equation for electrospray ionisation in TOF?

Answer 17

M(g) + H+ -> MH+(g)

Question 18

How can you calculate relative atomic mass?

Answer 18

(Mass of isotope 1 x %) + (Mass of isotope 2 x %) / 100

Question 19

What is the trend in ionisation energy down a group?

Answer 19

It decreases

Question 20

Why does ionisation energy change down a group?

Answer 20

It decrease because Atomic radius increases Shielding by inner electrons increases Less energy needed to remove the electron

Question 21

What is the trend in ionisation energy across a period?

Answer 21

It increases

Question 22

Why does ionisation energy change across a period?

Answer 22

It generally increases Atomic radius decreases Nuclear charge increases Shielding is the same More energy is needed to remove the electron.

Question 23

Which groups have difference in the trend for ionisation energy?

Answer 23

Group 3 and 6

Question 24

Why do group 3 and 6 have differences in ionisation energy?

Answer 24

Lower first ionisation energy than expected for group 3 and 6. Group 3 have s2, p1 arrangement P1 is further from the nucleus s2 electrons increase the shielding so less energy is needed to remove the p1 electron. Group 6 atoms have p4 arrangement – the repulsion of 2 electrons in the same p orbital leads to less energy being required to remove the outer electron.