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Chemistry > Structure of Atoms > Flashcards

Structure of Atoms Flashcards

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1
Q

What is atomic number?

A

The number of protons in the nucleus of an atom or an ion

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2
Q

What is mass number?

A

Total number of protons plus neutrons in the nucleus

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3
Q

How would you calculate the number of neutrons in an atom?

A

Mass Number - Atomic Number

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4
Q

Why do atoms have no overall charge?

A

Because the number of positively charged protons is equal to the number of negatively charged electrons.

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5
Q

Why is there an overall charge on an ION?

A

There will be an unequal number of positive and negative charges.

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6
Q

What is an isotope?

A

Atoms with the same number of protons but a different number of neutrons.

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7
Q

Are the chemical properties of isotopes different?

A

No because the number of electrons is the same

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8
Q

What is the mass and charge on an electron?

A

1/1800 and -1

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9
Q

What is the mass and charge on a proton?

A

1 and +1

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10
Q

What is the mass and charge on a neutron?

A

1 and 0

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11
Q

What is relative atomic mass?

A

The average mass of an atom of an element relative to 1/12th the mass of carbon-12.

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12
Q

What is meant by the first ionisation energy?

A

The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of ions with a single positive charge (+1)

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13
Q

What is meant by atomic radius?

A

The distance from the centre of the nucleus to the outer electrons of an atom.

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14
Q

What is meant by relative molecular mass?

A

Average mass of a molecule compared with 1/12th the mass of an atom of carbon-12

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15
Q

What is meant by relative formula mass?

A

Average mass of an entity relative to 1/12th the mass of an atom of carbon-12

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16
Q

What is an energy level?

A

Collection of sub shells with the same principle number

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17
Q

What is a sub-shell?

A

Collection of similarly shaped orbitals

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18
Q

What is an orbital?

A

Most likely place to find 2 electrons with opposing spins

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19
Q

What are the 3 sub shells?

A

S, P, D

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20
Q

State the number of orbitals and the max. no. of electrons in the S sub shells?

A

1 orbital and max. 2 electrons

21
Q

State the number of orbitals and max. number of electrons in the P sub shell?

A

3 orbitals and a max. of 6 electrons

22
Q

State the number of orbitals and max. électron number in the D sub shell?

A

5 orbitals and max 10 electrons

23
Q

Shape of s orbital

A

Spherical

24
Q

Shape of P orbital

A

Dumbbell

25
Q

Shape of D orbital

A

Various some are clover leaf like

26
Q

Électron arrangement?

A

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6

27
Q

Why is the 4s orbital filled before the 3D orbital?

A

4s has lower energy

28
Q

Units for ionisation energy?

A

kJmol–1

29
Q

What is the equation for the first ionisation of Sodium?

A

Na(g) —> Na+(g) + e- (g)

30
Q

What is meant by a successive ionisation energy?

A

Idea that: 1st electron requires the least energy to remove as it is removed from a neutral atom.
Removal of electrons after this require successively more energy to be removed (as electron is removed from +1,2,3, etc.)

31
Q

Describe change in ionisation energies down a group?

A

Ionisation energy decreases, easier to remove because negative electrons are further away from the positive pull of the nucleus

32
Q

3 reasons for the trend in ionisation energies down a group?

A

1/ large atomic radius so electrons will be further from the nucleus
2/ larger amount of shielding of nucleic charge
3/ increase in proton number (large charge) - counteracted by other 2 factors though !!!

33
Q

Describe the general trend in ionisation energies across a period?

A

It increases (generally) excluding group 3 and 6

34
Q

Give 3 reasons for the trend in ionisation energies across a period?

A

1/ increase in proton number (higher nuclear charge)
2/ same or similar atomic radius
3/ outer electrons pulled in closer so there is a greater attraction between the nucleus and outer most electrons

35
Q

Reason for dip in ionisation energies between groups 2 and 3? (Mg and Al)

A

Outer electrons of Al in 3p orbital which has slightly higher level than 3s orbital (which Mg outer electron is in) so requires less energy to remove.

36
Q

Reason for dip in ionisation energy between group 5 and 6 (P and S)?

A

P: sub shell in 3p contain 1 electron
S: one of the sub shells begins to pair with another electrons so contains 2 electrons so it’s easier to remove due to extra repulsion between negatively charged electrons.

37
Q

Factors affection ionisation energies?

A

Nuclear charge, distance from nucleus and shielding

38
Q

Do all isotopes have the same chemical properties? Why?

A

Yes because they have the same electron arrangement

39
Q

Why are there only 2 electrons in the first shell?

A

Due to small radius of shell the electrons would repel.

40
Q

What are atoms?

A

Smallest chemically divisible unit of an element

41
Q

What is ionisation ?

A

Process by which atoms lose/gain electrons to become ions

42
Q

What was John Daltons model of the atom?

A

He described atoms as solid spheres

43
Q

What was J.J Thomson model of the atom?

A

He concluded that the atom must contain small negatively charged particles (electrons). This new model was known as the plum pudding model.

44
Q

How did Ernest Rutherford come up with his?

A

They fired alpha particles at a very thin sheet of gold. From the plum pudding model they were expecting most of the particles to be deflected slightly however most of them passed straight through. Therefore he concluded that the atom has a tiny positively charged nucleus surrounded by a cloud of electrons and most of the atom was empty space.

45
Q

What is the Bohr’s model?

A

New model:
Electrons only exist in fixed orbitals
Each shell has fixed energy
When electron moves between shells electromagnetic radiation is emitted or absorbed
Because energy of shells is fixed the radiation will have a fixed frequency.

46
Q

Describe electron bombardment?

A

A sample is vaporise and high energy electrons are fired at it from an electron gun, usually knocking off 1 electron to form a +1 ions.

47
Q

How does a mass spectrometer work?

A
  1. Electrospray ionisation - sample is dissolved in a volatile solution and pushed through a fine hypodermic needle to produce a fine mist which is subjected to a high voltage.
  2. Acceleration - the +ve ions are accelerated by an electric field. This gives the same kinetic energy to all the ions. However the speed at which they travel is inversely proportional to their mass.
  3. Ion Drift - ions leave the electric field with a constant speed and contant kinetic energy. Ions with a lower mass/charge ratio wil, be drifting at higher speeds.
  4. Deflection - lighter ions travel faster so reach the detector in less time than heavier one. Therefore this data is used to calculate the mass/charge values needed to produce a mass spectrum.
48
Q

What is a mass spectrum?

A

Chart produced by a mass spectrometer. Height of each peak of graph shows the relative isotopic abundance.

49
Q

What are the rules for electron configurations?

A
  1. Electrons fill up lowest energy sub-shells first.
  2. Electrons fill orbitals in a sub shell singly before they start pairing
  3. For the configuration of ions, just add or remove the electrons to or from the highest energy occupied sub shell

Chemistry (2 decks)

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