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Chemistry unit 1 > unit 1.2 basic ideas about atoms > Flashcards

unit 1.2 basic ideas about atoms Flashcards

1
Q

Relative mass of proton?

A

+1

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2
Q

Relative mass of neutron?

A

+1

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3
Q

Relative mass of electron?

A

0

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4
Q

Relative mass of electron?

A

1/1840

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5
Q

Relative charge of proton?

A

+1

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6
Q

Relative charge of neutron?

A

0

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7
Q

Relative charge of electron?

A

-1

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8
Q

why is an atom always neutral?

A

number of positive protons and negative
electrons in an atom is always the same.

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9
Q

number of protons?

A

atomic number

bottom given in the element in the periodic table

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10
Q

number of electrons?

A

number of protons

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11
Q

number of neutrons?

A

mass number - atomic number

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12
Q

Atom?

A

smallest indivisible amount of an element. Atoms = neutral particles because the number of protons in the atom = the number of the electrons

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13
Q

Molecule?

A

Atoms bonded together. Molecules have no charge. Simplest molecule is diatomic eg Cl2

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14
Q

ions?

A

a charged particle. Metal ions = positive cation. Ca2+ whilst non metal ions are negative(anion) cl-

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15
Q

Isotopes?

A

atoms of the same element with a different number of eneutrons. Isotopes have the same atomic number but different mass number but different mass numbers but are chemically identical. all elements have isotopes more than 2

what is the difference between 37 Cl and 35 Cl?

35 Cl has 2 more neutrons

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16
Q

alpha?

A

2 protons and 2 neutrons. often called a helium nucleus

4
He or 4 2A
2
attracted to the negative plate
deflated in one direction
least penetrating power stopped by a sheet of paper

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17
Q

beta?

A

a fast moving electron
o
e attracted to the positive plate
1-
deflected in the opposite direction to alpha
stopped by a thin layer of metal

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18
Q

Gamma?

A

High electromagnetic radiation
Y
no effect on electric field
no effect on magnetic field
most penetrating - may need at least 2cm of lead to stop it

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19
Q

Gamma radiation?

A

has no effect on the mass and atomic number of the atom that emits it. This is
because it is a form of energy and is not an atomic particle.

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20
Q

alpha particles?

A

when emitted, cause the mass number to decrease by 4 and the atomic
number to decrease by 2.

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21
Q

beta radiation?

A

When an atom emits a particle of beta radiation, then its mass number is unchanged and the
atomic number increases by 1.

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22
Q

Electron capture?

A

one of the electrons is captured by a proton, turning it into a neutron.
An electron neutrino is emitted (ve). Atomic number goes down by one here due to the
changing of the proton into a neutron.

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23
Q

positron emission (β+ decay)

A

Here, a proton is converted to a
neutron, whilst releasing a positron and an electron neutrino. The positron is a type of beta particle
(β+). Atomic number goes down by one here as a proton is again changed into something else.

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24
Q

Radioisotope?

A

an isotope of an element which is radioactive eg carbon 14. atoms that are radioactive decay to become more stable due to unstable nuclei

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25
Q

Half life?

A

time it takes for half of the
atoms in a radioactive sample to decay

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26
Q

Transmutation?

A

alpha and beta emissions result in 1 element changing into a more new stable element

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27
Q

what is the use for radioactivity in medicine?

A

cobalt - 60 in radiotherapy for the treatment of cancer. The high energy of y- radiation = used to kill cancer cells and prevent the malignant tumour from developing.
iodine 131 for patients with defective thyroid glands. The iodine -131 acts as a tracer to study the uptake of iodine in the gland
technetium-99m = the most commonely used medical radioisotope. it is used as a tracer, normally to label a molecule which is preferentially taken up by the tissue to be studied

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28
Q

what is the use for radioactivity in radio dating?

A

Carbon 14 - used to calculate the age of plant and animal remains
all living organisms absorb carbon which includes a small proportion of carbon 14

Potassium 40 -used to estimate the geological age of rocks
can change into argon - 40 by the nucleus gaining in an inner electron

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29
Q

What is dilution anylasis?

A

isotopically labelled substances to find the mass of a substance in a mixture.
useful when a component of a complex mixture can be isolated from the mixture in the pure state but cannot be extracted quantitavely

30
Q

Monitoring the thickness of metal strips?

A

metal = placed between 2 rollers to get the right thickness
a radioactive source = mounted one of side of the metal with a detector on the other

31
Q

Monitoring the thickness of metal strips?

A

metal = placed between 2 rollers to get the right thickness
a radioactive source = mounted one of side of the metal with a detector on the other

32
Q

Electronic structure?

A

electrons within atoms occupy fixed energy levels or shells
shells = 1,2,3,4 etc. Numbers = principal quantum

33
Q

Atomic orbital?

A

region in an atom that can hold up to 2 electrons with opposite spins

34
Q

what are the 4 different types of orbitals?

A

s,p,d and f

35
Q

what is subshell?

A

where orbitals of the same type are grouped together

36
Q

what orbital is a S?

A

spherical and can contain 2 electrons

37
Q

what orbital is a P?

A

made up of 3 dumb bell shaped lobes mutually at right angles and are seperated into 3 types: px orbital, py orbital and pz orbital

38
Q

how much electrons can each p orbital hold?

A

2 electrons

39
Q

how much electrons can each p subshell hold?

A

6 electrons

40
Q

how much electrons an 5 d orbitals hold

A

10 electrons in a d subshell

41
Q

what is the way in which electrons are arranged ?

A

called electronic structure or configuration

42
Q

how can this be worked out via 3 rules?

A

electrons fill atomic orbitals in order of increasing energy
maximum of 2 electrons can occupy any orbital each with opposite spins
each orbital in a subshell will first fill with 1 electron before pairing starts

43
Q

what is the most common way of representing electronic structure?

A

to write the shell number first, followed by the orbital letter and then the number of electrons in the orbital

44
Q

how does this apply to nitrogen?

A

2 electrons in the s orbital in the 1st shell
2 electrons in the s orbital in the 2nd shell
3 electrons in the p orbital in the 2nd shell
so the electronic configuration = 1s^22s^2p^3

45
Q

what about calcium?

A

20 electrons , electronic configuration = 1s^22s^22p^63s^23p^64s^2

46
Q

how do positive ions form?

A

by the loss of electrons from the highest energy orbitals so these fewer electrons than the parent atom

47
Q

how do negative ions form?

A

by adding electrons to the highest energy orbitals so the ions have more electrons than the present atom

48
Q

ionisation?

A

the process of removing electrons from an atom

49
Q

Equation for process of first ionisation energy?

A

x(g) ——– x+(g) +e-

50
Q

first ionsisation energy?

A

electrons = held in their shells by their attraction to the positive nucleus , therefore the greater the attraction, the greater the ionisation energy.

51
Q

What does this depend on?

A
  1. shielding - an increase in shielding will decrese I-E. full inner shells of electrons reduce the attraction of the nucleus on outer shell electrons
    An increase in shielding outweighs an increase in nuclearcharge.
    Shielding increases down a group but remains constant across a period
  2. Nuclear charge (proton number). An increase in nuclear charge across a period usually increases IE. Nuclear charge increases across a period and down a group. However shielding = more important than nuclear charge
  3. Atomic radius. The further the distance of an electron from an atom’s nucleus the lower the IE. Atoms get larger descending a group But smaller across a period
  4. s subshell shielding. a p subshell in the same subshell
  5. an occupieds susbhell sheild p electrons in the same shell. e.g 2s^2 shielding 2p^1. this sometimes outweighs an increase in nuclear charge
  6. electron pair repulsion in a p subshell. a p orbital occupied by a pair of electrons exhibits electron pair repulsion whereas p oribtal with an unpaired electron shows no repulsion.
    hence, sometimes an increase in nuclear charge is outweighed by this electron pair repulsion.
52
Q

what are successive ionisation energies a measure of?

A

the energy needed to remove each electron in turn until all the electrons = removed from an atom

53
Q

how many ionisation energies does an element have?

A

the number of electrons it has

54
Q

how do successive ionisation energies increase?

A

greater effective nuclear charge as the same number of protons are holding fewer and fewer electrons
as each other electron = removed, there = less electron - electron repulsion and each shell will be drawn slightly closer to the nucleus
as the distance of each electron from the nucleus decreases, the nuclear attraction increases

55
Q

successive ionisation energies of sodium?

A

there is 1 electron on its own which is easiest to remove
8 more electrons which become successively more difficult to remove
2 electrons which = the
most difficult to remove
large increase in ionisation energy as the 2nd and 10th electrons = removed. if all electrons were in the same shell, there would be no rise or jump

56
Q

what is light a form of?

A

electromagnetic radiation
c = f(lander)

57
Q

what is the frequency of electromagnetic radiation + energy connected by:

A

E=hf
therefore if frequency increases, energy increases
f = directly proportional to 1/lander + if frequency increases, wavelength decreases

58
Q

what is the whole range of frequencies of electromagnetic radiation called?

A

the electromagnetic spectrum

59
Q

absorption spectra?

A

light of all visible wavelengths = called white light
when white light = passed through the vapor of an element certain wavelength will be absorbed by the atoms + removed from the light.
black lines appear in the spectrum where light of some wavelengths has been absorbed. wavelengths of these lines correspond to the energy taken in by the atoms to promote electrons from lower to higher energy levels

60
Q

Emission spectra?

A

when atoms = given energy by heating or by an electrical field, electrons = promoted from a lower energy level to a higher one
when the source of energy = removed, the electrons fall from a higher energy level to a lower energy level + the energy cost = released as a packet of energy called a quantum of energy
corresponds to electromagnetic radiation of a specific frequency
the observed spectrum consists of a number of coloured lines on a black background

61
Q

How does the hydrogen spectrum work?

A

an atom of hydrogen has only 1 electron so gives the simplest emission spectrum

62
Q

what does the atomic spectrum of hydrogen consist of?

A

seperate series of lines mainly in the UV, visible + infrared regions of the electromagnetic spectrum

63
Q

how does electromagnetic radiation come about?

A

when an atom = exited by absorbing energy, an electron jumps to a higher energy level. As the electron falls down to a lower energy level, emits in the form of electromagnetic radiation. Emitted energy can be seen as a line in the spectrum because this is = to the difference between the 2 energy levels.

64
Q

what happens as the frequency increases?

A

the lines get closer together because the energy difference between the shells decreases

65
Q

what is each line of the lyman series for?

A

due to electrons returning to the first shell or n = 1 energy level while the balmer series = electrons returning to the n =2 energy level

66
Q

describe the ionisation of the hydrogen atom

A

the spectral lines become closer + closer together as the frequency of the radiation increases until they converge to a limit
the convergence limit corresponds to the point at which the energy of an electron = no longer quantised. At that point, the nucleus has lost all influence over the electron ; the atom = ionised

67
Q

what does measuring the convergent frequency of the lyman series do?

A

allows the ionisation energy to be calculated
value of deltaE = multiplied by the Avogadro’s constnt to give the first ionisation energy for a mole of atoms

68
Q

comparing elements in the same group

why does K have a lower IE then Li

K = 1s2 2s2 2P6 3S2 3P6 4S1
Li = 1s2 2s1

A

Potassium’s outer 4s electron is further away from the positive attraction of the nucleus with more shielding compared to lithiums outer 2s electron
these 2 factors outweigh the increase in nuclear charge Li to K
hence less energy is required to remove the 4 s electron in a K atom compared to a 2s electron in a Li atom

69
Q

comparing elements in the same period

why F has a hiher first IE compared to Li

F = 1s2 2s2 2p5
Li= 1s2 2s1

A

flourine has a smaller atom with greater nuclear charge with no difference in shielding compared to lithium
hence more energy = required to remove an outer shell 2p electron in F compared to 2s electron in Li

70
Q

explaining the discrepancy group 2 vs group 3

boron 1st Ie should be higher than Be but this isnt correct

Be = 1s2 2s2
B = 2s2 2S2 2P1

A

Less energy = required to remove the outer 2p electron in boron compared to removing one of the spin paired 2s electrons in beryllium
this is because the increase in nuclear charge Be to B = outweighed by the 2s subshell in boron shielding the outer 2p electron.
in addition, the outer 2p electron in B is further away from the positive attraction of the nucleus compared to Be

Chemistry unit 1 (4 decks)

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