Atomic Structure and Nuclear Chemistry

Question 1

Why are atoms neutral?

Answer 1

They have the same number of protons and electrons

Question 2

What happens to an atom if you change the number of protons or electrons?

Answer 2

You get a charged ion

Question 3

What is the atomic number (Z)?

Answer 3

The number of protons in the nucleus of the atom

Question 4

What is the mass number (A)?

Answer 4

The sum of protons and neutrons in the nucleus (nucleon number)

Question 5

How are electrons arranged?

Answer 5

They surround the nucleus in orbitals and orbitals are grouped into families called shells

Question 6

What are orbitals?

Answer 6

Specific regions of space

Question 7

What do atoms with the same number of outermost electrons have in common?

Answer 7

Outermost electrons determine the properties of an atom, they will have similar reactivity and ability to form bonds

Question 8

What is an isotope?

Answer 8

Atoms with the same atomic number but a different mass number (or the same number of protons but a different number of neutrons)

Question 9

Do different isotopes of an atom have identical chemical properties?

Answer 9

Yes, they have the same outer electrons and chemical identity

Question 10

What is the kinetic isotope effect?

Answer 10

Means heavier isotopes react slightly more slowly

Question 11

What differs between isotopes of the same atom?

Answer 11

Physical properties such as density

Question 12

What are the three isotopes of Hydrogen and give a use of each isotope

Answer 12

H-1 (Protium): most abundant isotope
H-2 (Deuterium): Used in isotopic labelling experiments; very useful in NMR spectroscopy
H-3 (Tritium): Radioactive; used in labelling experiments

Question 13

What are the isotopes of chlorine?

Answer 13

Cl-35 and Cl-37

Question 14

What are the isotopes of bromine?

Answer 14

Br-79 and Br-81 and at least 23 further unstable isotopes

Question 15

How is RAM calculated in terms of isotopes?

Answer 15

It’s the weighted average of the individual isotopes

Question 16

How is RAM of chlorine calculated?

Answer 16

There are 3 atoms of Cl-35 to every 1 atom of Cl-37 in ordinary chlorine.
So, (3x35) + (1x37)/4 = 35.5

Question 17

Describe a stable isotope

Answer 17

Remain unchanged indefinitely

Question 18

Describe an unstable isotope

Answer 18

Undergo spontaneous disintegration in order to become a stable nucleus.
Disintegration results in emission of small particles and/or radiation.
Also called radioactive isotopes

Question 19

What is a feature of both unstable and stable isotopes?

Answer 19

Both can be used as diagnostic tools and tracers in scientific research

Question 20

What is mass spectrometry?

Answer 20

Measures the molecular weight of atoms or compounds by observing the mass to charge ratio (m/z) of atoms

Question 21

How does mass spectrometry work?

Answer 21

Atoms and molecules are converted into ions, which can be separated on the basis of their masses and motions in magnetic or electrical fields

Question 22

Does mass spectrometry work for unstable or stable isotopes?

Answer 22

Both

Question 23

What are applications of mass spectrometry?

Answer 23

Determining isotopic abundances and the identity of small molecules and proteins