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Chemistry > 1) Atomic structure > Flashcards

1) Atomic structure Flashcards

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1
Q

Atoms

A

mostly empty space surrounding a very small, dense nucleus that contains protons and neutrons, electrons are found in shells in the empty space around the nucleus

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2
Q

Table of subatomic particles

A

in notes

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3
Q

Atomic/proton number

A
  • number of protons in the nucleus of an atom
  • calculated by mass-neutrons
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4
Q

Mass/nucleon number

A
  • total number of protons + neutrons in the nucleus of an atom
  • calculated by mass number-atomic number
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5
Q

Electrons

A
  • same number as protons
  • a positively charged ion has lost electrons and a negatively charged ion has gained electrons
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6
Q

Distribution of mass and charge within an atom

A
  • the mass of an atom is concentrated as it contains the protons and neutrons in the positively charged nucleus which is attracted to the negatively charged electrons orbiting around it
  • the electrostatic attraction between the + nucleus and negatively charged electrons orbiting around it, is what holds the atom together
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7
Q

Protons in an electric field

A
  • a beam of protons is deflected away from the + plate, towards the - plate
  • proves that protons are positively charged
  • as protons are deflected less than electrons this shows that protons are heavier than electrons
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8
Q

Neutrons in an electric field

A
  • a beam of neutrons is not deflected at all
  • proves that the particle is neutral and is not attracted to or repelled by the - or + plate
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9
Q

Electrons in an electric field

A
  • a beam of electrons is fired past the electrically charged plates and deflected very easily away from the - plate towards the + plate
  • proves that electrons are negative and that they have a very small mass
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10
Q

Atomic radius

A

a measure of the size of an atom and is half the distance between the 2 nuclei of 2 covalently bonded atoms of the same type

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11
Q

Trend across the period

A
  • atomic radius decreases
  • ionisation energy increases
  • nuclear charge increases
  • shielding remains relatively constant
  • shell number is the same
  • attraction between nucleus and electrons increases
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12
Q

Trends down the group

A
  • atomic radius increases
  • ionisation energy decreases
  • nuclear charge increases
  • shielding increases
  • shell number increases
  • attraction between nucleus and electrons decreases
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13
Q

Atomic radius decreases as you move across the period because…

A
  • atomic number increases (increased positive nuclear charge) but at the same time extra electrons are added to the same principal quantum shell
  • the larger the nuclear charge, the greater the pull of the nuclei on the electrons which results in smaller atoms
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14
Q

Atomic radius increases down the group because …

A
  • increased number of shells
  • electrons in the inner shells repel the electrons in the outermost shells, shielding them from the + nuclear charge and this weakens the pull of the nuclei on the electrons, resulting in larger atoms
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15
Q

Atomic radius increases at end of one period and beginning of the next period, because …

A
  • increases between the noble gas end of each period and the alkali metal at the beginning of the next period as it has one extra principal quantum shell which increases shielding of the outermost electrons
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16
Q

Ionic radius

A

a measure of the size of an ion

17
Q

Ionic radius increases with increase - charge, because…

A
  • ions with - charges are formed by atoms accepting electrons while the nuclear charge remains the same
  • the outermost electrons are further away from the + charged nucleus and are therefore held only weakly to the nucleus, which increases the ionic radius
  • the greater the negative charge, the larger the ionic radius
18
Q

Ionic radius decreases with increasing + charge, because…

A
  • positively charged ions are formed by atoms losing electrons
  • the nuclear charge remains the same, but there are now fewer electrons that undergo a greater electrostatic force of attraction to the nucleus, which decreases the ionic radius
  • the greater the positive charge, the smaller the ionic radius
19
Q

Ionisation energy (IE)

A

the amount of energy required to remove 1 mole of electrons from 1 mole of gaseous atoms of an element to form 1 mole of gaseous ions

20
Q

First ionisation energy (IE1)

A

the energy required to remove 1 mole of electrons from 1 mole of atoms of an element to form 1 mole of 1+ ions

Ca (g) = Ca+ (g) + e-

21
Q

Factors that influence the ionisation energy of elements

A

1) Nuclear charge
2) Atomic/ionic radius
3) Shielding by inner shells and sub-shells
4) Spin-pair repulsion

22
Q

Ionisation energy increases across the period, because…

A
  • nuclear charge increases
  • causes atomic radius of the atoms to decrease as the outer shell is pulled closer to the nucleus therefore the distance between the nucleus and outer shell electrons decrease
  • shielding by inner electrons remains relatively constant as electrons are being added to the same shell
  • it therefore becomes harder to remove an electron and more energy is needed
23
Q

Ionisation energy decreases down the group, because…

A
  • number of protons in the atoms increases therefore nuclear charge increases
  • however the atomic radius of the atoms increase as you are adding shells which makes the atom bigger
  • so distance between the nucleus and outer electrons increase
  • shielding by inner electrons increase as there are more shells
  • these factors outweigh the increased nuclear charge, therefore it becomes easier to remove the outer electron
24
Q

Ionisation energy decreases from one period to the next, because..

A
  • increased distance between the nucleus and outer electrons as you have added a new shell
  • there is increased shielding by inner electrons due to the added shell
  • the above 2 factors outweigh the increased nuclear charge
25
Q

Successive ionisation energies of an element increase, because..

A
  • once you have removed the outer electron from an atom, you have formed a positive ion
  • removing an electron from a + ion is more difficult than from a neutral atom
  • as more electrons are removed, the attractive forces increase due to decreasing shielding and an increase in the proton to electron ratio
  • the increase in ionisation energy however is not constant and is dependent on the atoms electronic configuration
26
Q

First ionisation energy in detail

A
  • first electron removed has a low IE1 as it is easily removed from the atom due to the spin-pair repulsion of the electron in the 4s orbital
  • the second electron is more difficult to remove than the 1st as there is no spin-pair repulsion
  • the third electron is much more difficult to remove than the second as the third electron is in a principal quantum shell which is closer to the nucleus (3p)
  • removal of the fourth electron is more difficult as the orbital is no longer full and there is less spin-pair repulsion
27
Q

First ionisation energy increases across the period, because …

A
  • number of protons in the nucleus increases, leading to a stronger positive charge in the nucleus
  • electrons are added to the same principal quantum shell so shielding remains relatively constant
  • due to increased nuclear charge and constant shielding, attraction between the nucleus and outer electrons increases, making it harder to remove an electron
28
Q

Deducing the position and electronic configuration of an element using successive ionisation energy data

A
  • by analysing where the large jump occurs and the number of electrons removed when these large jumps occur
29
Q

Isotope

A
  • atoms of the same element that contain the same number of protons and electrons, but a different number of neutrons
30
Q

Chemical and physical properties of an isotope

A

Chemical- same, as they have the same number of electrons in their outer shell and electrons take part in chemical reactions

Physical- different, as the only difference between isotopes is the number of neutrons and because they only add mass to the atom, isotopes have different masses and densities

31
Q

Shells

A

regions surrounding the atomic nucleus containing a specific number of electrons

32
Q

Subshells

A
  • the principal quantum shells are split into subshells (s, p, d, f)
  • s > p > d > f
  • however the 3d orbital has a slightly higher energy than the 4s orbital and because of this the 4s orbital is filled before the 3d orbital
33
Q

Orbitals

A
  • each atomic orbital can be occupied by a maximum of 2 electrons

s: 1 orbital (2 electrons)
p: 3 orbitals (6 electrons)
d: 5 orbitals (10 electrons)
f: 7 orbitals (14 electrons)

34
Q

Principal quantum number (n)

A
  • used to number the energy levels or quantum shells
  • the lower this number, the closer the shell is to the nucleus n=1: up to 2 electrons
    n=2: up to 8 electrons
    n=3: up to 18 electrons
    n=4: up to 32 electrons
35
Q

Ground state

A
  • the most stable electronic configuration of an atom which has the lowest amount of energy
  • achieved by filling the subshells of energy with the lowest energy first (1s)
  • orbitals in the same subshell have the same energy and are said to be degenerate
36
Q

Electronic configurations

A
  • electrons with similar spin repel each other (spin-pair repulsion)
  • electrons therefore occupy separate orbitals in the same subshell to minimise this repulsion and have their spin in the same direction
  • electrons are only paired when they are no more empty orbitals available within a subshell, in which case the spins are the opposite spins to minimize repulsion
  • energy required to jump to a successive empty orbital is greater than the inner electron repulsion and they therefore pair up and occupy the lower energy levels first
37
Q

Determining electronic configurations of atoms and ions

A

examples in notes

38
Q

Box notation

A

in notes

39
Q

Free radical

A
  • a species with 1 or more unpaired electrons
  • unpaired electron is shown as a dot
  • formed when a molecule undergoes homolytic fission where the 2 electrons of a covalent bond are split evenly between the 2 atoms

Chemistry (19 decks)

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