chem-radioactivity

Question 1

calculate the Ar of this: 50.1% , Cu-63, 49.9% Cu-64

Answer 1

63.499

Question 2

calculate the empirical formula of Mg(0.72g) and O(0.48g).

Answer 2

calculate moles by dividing mass by mr and then divide the moles of both by the one that has the smallest moles.

Question 3

what did the big bang form

Answer 3

H, He,Li nuclei (10^8 degrees celcius is the temperature)

Question 4

when did the universe cool

Answer 4

10,000 years later (10^8 degrees celcius what it cooled to)

Question 5

what happened to gas clouds

Answer 5

became compressed and hot and triggered nuclear reactions.

Question 6

what happens to electrons at high temperature

Answer 6

form plasma ( ionised atoms and unbound electrons)

Question 7

what do nuclear reactions involve

Answer 7

change in the nucleus of the atom

Question 8

what can happen to an element in nuclear reactions

Answer 8

it can change into another

Question 9

whats nuclear fusion

Answer 9

two lighter nuclei combine to form a heavier nuclei.

Question 10

what is needed to overcome replusion between +ve charges on the the two nuclei

Answer 10

high speed and large amounts of kinetic energy.

Question 11

what does H turn into

Answer 11

He , releases a lot of energy

Question 12

why do heavy stars have further fusion reactions and form heavier nuclei

Answer 12

because of the high temperature and pressure

Question 13

what will the core contain over millions of years

Answer 13

He,C , Ne , Si , Fe

Question 14

what does the Fe core do when its mainly Fe

Answer 14

since fe absorbs energy when its mainly Fe the core explodes causing a supernovae

Question 15

what does a suprernovae do

Answer 15

disperses the elements into the universe

Question 16

is the nuclei of some atoms of a particular isotope stable

Answer 16

no, its unstable

Question 17

the nuclei of some atoms can break down… + whats this called

Answer 17

forming new elements , radioactive decay.

Question 18

what are atoms thats nuclei break down forming new elements called

Answer 18

radioactive

Question 19

what are the isotopes that nuclei break down forming new elements called

Answer 19

radioisotopes

Question 20

how do they break down

Answer 20

spontaneously

Question 21

what happens when the nuclei breaks down

Answer 21

emits rays and particles

Question 22

what do these rays and particles do

Answer 22

knock off electrons from atoms , they collide with ionising radiation

Question 23

what are the main radioactive processes

Answer 23

alpha decay , beta decay , gamma emission

Question 24

what’s alpha decay

Answer 24

the nucleus emits an alpha particle which is a group of 2 protons and neutrons.

Question 25

what’s the difference between nuclei and nucleus

Question 26

whats beta decay

Answer 26

an electron called a beta particle is emmited from the nucleus

Question 27

what’s gamma emission

Answer 27

high energy EM radiation is emitted from the nucleus, often occurs alongside alpha and beta decay

Question 28

learn the symbols of alpha decay, beta decay and gamma emission

Answer 28

online

Question 29

what element has the same nucleus as an alpha particle

Answer 29

helium

Question 30

what is an alpha particle written as

Answer 30

online

Question 31

whats an alpha particle made up of

Answer 31

2 protons and 2 neutrons

Question 32

what happens when its emitted from the nucleus of an atom

Answer 32

the atomic number of that element goes down by two and the mass number by 4 , changing it into a new element

Question 33

whats a beta particle

Answer 33

an electron

Question 34

how is it written

Answer 34

check online

Question 35

where is it emitted from

Answer 35

the nucleus , not the electron shells

Question 36

how is a beta particle (an electron) emitted from the nucleus? 3 steps

Answer 36

a neutron turns into a proton and electron.

the proton formed stays in the nucleus , electron is ejected.

a new element is created with the same mass number but the atomic number is +1 then the og element because it ‘gained an electron’.

Question 37

whats gamma emission

Answer 37

emission of energy from the nucleus , but no new elements are formed

Question 38

is radioactive decay a random process

Answer 38

yes

Question 39

decay is independent from?

Answer 39

chemical or physical state

Question 40

what happens as more of the nuclei decays

Answer 40

the sample becomes less radioactive.

Question 41

what’s half life

Answer 41

time taken for half the nuclei to decay

Question 42

radioactive half life is fixed….

Answer 42

for a given isotope

Question 43

what happens in nuclear fusion

Answer 43

two lighter nuclei combine to form a heavier nuclei

Question 44

what conditions are needed for nuclear fusion

Answer 44

high temperature and pressure to overcome the repulsion of positive charges between both of the nuclei

Question 45

how are certain elements formed inside stars

Answer 45

by nuclear fusion

Question 46

whats the charge and mass of an alpha particle

Answer 46

+2, 4

Question 47

whats is an alpha particle stopped by and whats its deflection by electric field

Answer 47

paper, small deflection by electric field

Question 48

whats the charge and mass of a beta particle

Answer 48

-1 , negligible(very small)

Question 49

whats a beta particle stopped by and its deflection by electric field

Answer 49

aluminium foil, large

Question 50

why is there no significant health risk in normal usage of smoke detectors

Answer 50

the dose of radiation is to small to cause a health risk

Question 51

how do alpha particles cause the ionisation of air molecules in the smoke detector

Answer 51

alpha particles collide with molecules and knock off electrons.