Atomic Theory

Question 1

Define radioactivity.

Answer 1

Radioactivity is the spontaneous breaking up of an unstable nucleas with the emission of one or more types of radiation.

Question 2

Explain Heisenberg’s uncertainty principle.

Answer 2

The more closely you are to knowing the position of an electron the further you are from knowing it’s velocity.

Question 3

Electronegativity down a group.

Answer 3

~Shielding effect

~Bigger atomic radius

Question 4

Electronegativity across a group

Answer 4

~Increases
~Increase in nuclear charge
~Smaller atomic radius

Question 5

Define half life.

Answer 5

Time taken for half of the nuclei in a sample to decay.

Question 6

What’s atomic mass?

Answer 6

Number of protons in the nucleas of an atom.

Question 7

The trend in electronegativity values down the first group of elements.

Answer 7

EN vales decrease down group because of shielding effect.

Question 8

Define orbitals

Answer 8

Region in the space around the nucleas of an atom which electrons are most likely to be found.

Question 9

Relative atomic mass

Answer 9

The average mass of an element as it occurs in nature compared to 1/12 of the mass of a 12 carbon isotope.

Question 10

What is electronegativity?

Answer 10

Measure of attractiveness an atom has for a shared pair of electrons in a covalent bond.

Question 11

What is the first ionisation energy?

Answer 11

Minimum energy required to remove the most loosely bound electron form an atom in its ground state.

Question 12

What is molar mass?

Answer 12

The mass in grams of a mole of that substance.

Question 13

What is atomic radius ?

Answer 13

Half the distance between the nuclei of two singly covalenty bonded atoms./ of two identical atoms joined by a single covalent bond

Question 14

What is mass number?

Answer 14

Number of protons+ neutrons

Question 15

Define isotopes

Answer 15

Atoms of the same element which have same number of protons but different numbers of neutrons.

Question 16

What was the purpose of Milikan’s oil drop experiment?

Answer 16

To determine the charge of an electron

Question 17

Name the scientist who identified cathode rays as a subatomic particle and also measure the charge to mass ratio?

Answer 17

J. J. Thompson

Question 18

Describe Thompson’s “plum pudding”

Answer 18

model of the atom which had negatively-charged electrons embedded within a positively-charged “soup”/ sphere

Question 19

Rutherford used alpha particles. What are these?

Answer 19

Helium nucleus. Two protons and two neutrons

Question 20

2 properties of cathode rays

Answer 20

Travel in straight lines/ negligible mass/ negatively charged

Question 21

State two assumptions of Dalton’s atomic theory of 1808

Answer 21

Atoms are small and indivisible

Question 22

Who measured the charge of the electron?

Answer 22

Millikan

Question 23

Who measured the ratio of charge to mass of an electron

Answer 23

J. J. Thompson

Question 24

What did Rutherford do?

Answer 24

Proved that electrons in an atom reside in an electron cloud surrounding a small dense positive nucleus

Question 25

Law of conservation of mass

Answer 25

When a chemical reaction takes place, matter is neither created or destroyed but merely changes from one form to another.

Question 26

Matter

Answer 26

Anything that occupies space and has mass.

Question 27

Relative molecular mass

Answer 27

Sum of relative atomic masses of all atoms in a molecule of the compound compared to 1/12 of the mass of a carbon-12 isotope

Question 28

Three fundamental processes that occurred in the mass spectrometer

Answer 28

Ionisation/ acceleration/ separation

Question 29

What result did Rutherford expect to get when thin gold foil was bombarded with alpha particles?

Answer 29

Alpha particles were expected to pass straight through/ Un deflected

Question 30

How did the actual result of Rutherford’s experiment differ from the expected result

Answer 30

Some particles were deflected at large angles /nuclease positive / almost all passed through/ some bounced straight back

Question 31

How was the model of atomic changed as a result of Rutherford’s experiment

Answer 31

Large electron cloud surrounding/ atoms mostly empty space/ nuclease very small

Question 32

Energy level

Answer 32

Shell which electrons of equal energy can occupy

Question 33

Aufbau principle

Answer 33

Electrons occupy the lowest available energy level

Question 34

What was Dalton’s atomic theory

Answer 34

Matter composed of atoms/ atoms are tiny particles/ atoms are indivisible/ cannot be created or destroyed

Question 35

What happens in a radioactive nuclease during beta decay?

Answer 35

Neutron changes into proton and an electron which is emitted

Question 36

How did Mendeleev arrange the elements in the periodic table of 1869?

Answer 36

According to atomic weight/ in groups of similarities properties

Question 37

How do we know that any new element discovered in the future will be super heavy

Answer 37

No gaps in modern periodic table/ all other lighter elements known

Question 38

Main energy levels in electron transition that gives rise to the first line of the balmer series in the emission spectrum of the hydrogen atom

Answer 38

3 and 2

Question 39

Describe trend in covalent radii for atoms of the second period of the periodic table

Answer 39

Increases because of additional shells/ increase in nuclear charge

Question 40

Term used for the condition of the hydrogen atom when its electron occupies any of the levels E2,E3,etc?

Answer 40

Excited state

Question 41

What causes the electron to leave the E1 level?

Answer 41

Acquires energy /heat

Question 42

Why does the electron not remain in any of the levels E2,E3,etc?

Answer 42

Higher energy states unstable

Question 43

How does modern atomic theory describe the behaviour of electrons?

Answer 43

Electrons have both wave and particle properties

Question 44

Cathode rays

Answer 44

Beams of electrons/ negatively charged

Question 45

Advantage of arranging elements in order of atomic number

Answer 45

Indicates gaps/ undiscovered elements / tellurium and iodine positions are justified

Question 46

Position of tellurium and iodine in the 1869 table

Answer 46

Listed according to chemical properties/ listing by atomic mass wouldn’t group them with elements of the similar properties

Question 47

Periodic system in context of Mendeleev’s 1869 table

Answer 47

Elements listed according to atomic mass/ properties repeat periodically

Question 48

Why the elements of group 18 in the table are chemically inert

Answer 48

Stable arrangement of electrons/ do not lose or gain electrons

Question 49

Scientist who discovered presence of cathode rays

Answer 49

Crookes( paddle wheel experiments)

Question 50

Who discovered the neutron?

Answer 50

Chadwick

Question 51

Give a reason for the general increase in first ionisation energy across a period of the periodic table

Answer 51

the increase in nuclear charge having a greater pull on the electrons and therefore more energy is required to remove electrons

Question 52

Explain why the general increase in first IE is interuppted

Answer 52

The repulsion between 2 electrons makes one of them easier to remove/ beacuse boron has a smaller value than baylium

Question 53

Mass spectrometer processes

Answer 53

1. Vaporitasion 2. Ionisation 3. Acceleration 4. Seperation 5. Detection 6. Display

Question 54

Describe ionisation process in mass spectrometer

Answer 54

The sample is ionised by bombarding it with high energy electrons

Question 55

Describe acceleration and sepearation in mass soectrometer (process 3&4)

Answer 55

Acceleartion: positive ions are accelerated by negatively charged plates. Seperation: ions are deflected by magnetic feild

Question 56

What is the last process in mass spectometer

Answer 56

Detection: ions are detected by a sensitive plate

Question 57

What are gamma particles?

Answer 57

Electromagnetic radiation. Highly penetrating