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Chemistry BMC ESE > SCT 1 > Flashcards

SCT 1 Flashcards

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1
Q

Elements?

A

Elements are pure substances that cannot be decomposed by any chemical means

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2
Q

physical properties

A

physical properties are characteristics of thee material that are determined without altering the chemical composition

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3
Q

Chemical properties

A

Chemical properties are the characteristics of the material that are determined by altering of the materials chemical composition allowing the material to decompose or react with other substances to forma new material

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4
Q

Mixture

A

A mixture is two or more substances mixed together but not chemically combined

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5
Q

Homogenous mixture

A

this is a type of mixture with uniform composition

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6
Q

heterogeneous mixture

A

This is a type of mixture with a non uniform composition and has clear physical derivatives

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7
Q

pure substance

A

cannot be separated two or more substances by physical means

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8
Q

law of mass conversion

A

Mass cannot be created or destroyed it can only be conserved.

Mass at reactants = mass oof products

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9
Q

law of definite proportions

A

Chemical compounds will always have a definite proportion of elements irrespective to the source of the compound.

so water from the toilet will have the same chemical composition of H20 as fresh after does

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10
Q

Daltons atomic theory

A
  1. Elements are made up of atoms
  2. Atom of the same element will have the same properties
  3. Compounds formed from the chemical combination of elements will have a fixed ratio
  4. Chemical reactions are thee rearrangement of atoms in order to form new compounds, atoms cannot be created nor destroyed
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11
Q

Problems with Dalton’s theory

A
  1. Elements are made of atoms and are indivisible particles - atoms can be divided, but only ina nuclear reaction
  2. All atoms of a particular element are similar - this does account for isotopes
  3. Compounds formed from the chemical combination of elements have a fixed ratio - correct
  4. Chemical reactions are the rearrangements of atoms in order to form new compounds, atoms cannot be created nor destroyed - except for nuclear reactions that can change atoms of one element to a different element
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12
Q

Formation of anions and cations

A

Cations - taking away an electron from an atom gives us an atom that has more protons than electrons and so has an overall positive charge

Anion - the adding of an electron too an atom gives us an atom with a greater number of electrons than protons and so has an overall negative charge

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13
Q

Chemical bonds

A

Chemical bonds are forces of attraction between ions atoms and molecules, chemical bonds join atoms together

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14
Q

Chemical bonds are formed for 2 reasons:

A
  1. Obtain stability

2. is obtain inert gas configuration: octet rule

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15
Q

Covalent bonds

A

Covalent bond results in the sharing of several electrons (usually two) between non-metals that form chemical bonds forming a compound

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16
Q

Ionic bonds

A

Ionic bonds are formed between a metal and a non-metal it is formed by the transfer of electrons from one atom to another.

one atom is reduced and the other is oxidized forming ions with opposite charges that attract to each other via their electrostatic forces of attraction forming an ionic bond

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17
Q

lattice structure

A

the ionic bond forms a lattice structure that is built up by the electrostatic attractions between the cations and anions.

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18
Q

Lattice energy

A

this is the energy found in the lattice structure and is what stabilizes the structure, the lattice energy, however, is inversely proportional to the distance between the atoms in a structure and so:

the greater the distance between the atoms in the structure meaning the greater the size of the structure meaning the weaker the lattice energy

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19
Q

will the lattice energy be stronger in large molecules or small molecules

A

The lattice energy will be stronger in smaller molecules as the distance between the atoms is less and so there are stronger electrostatic forces of attraction between the atoms valence electrons and the other atoms atomic nucleus making it harder to separate

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20
Q

SCT 2

A

hi :)

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21
Q

Spectroscopy

A

Spectroscopy is the study of the interaction between matter and radiant energy (electromagnetic energy)

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22
Q

electromagnetic spectrum

A

GXUVIMR - where Gamma rays have the highest frequency and lowest wavelength

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23
Q

Electromagnetic energy

A

The electromagnetic energy travelling through a vacuum behaves like waves

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24
Q

Electromagnetic energy can be characterized by 3 points:

A

wavelength, frequency and amplitude

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25
Q

Wavelength

A

This is the distance between two successive peaks

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26
Q

frequency

A

the number of successive waves that pass a point per unit of time

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27
Q

Amplitude

A
  • is the maximum height between the top of the wave and the centre

Amplitude is also defined as the intensity of the wave

  • the greater the max height (amplitude) the brighter the wave
  • the lower the max height the dimmer the wave.
28
Q

STUDY WAVE EQUATIONS

A

STUDY WAVE EQUATIONS

29
Q

2 forms of light

A

Monochromatic light: Radtion composed of just wavelength

continuous light: Radtion that is composed of multiple wavelengths

30
Q

Emission spectrum

A

is when a continuum of radiation is passed through an unexcited atom, the unexcited atom then absorbs only some wavelengths and not all. The continuum radiation continues to a detector where it shows the non-absorbed wavelengths and wavelengths that are absorbed appear as black gaps

31
Q

Absorption spectrum

A

the wavelengths absorbed by the excited atoms are radiated showing us the absorbed wavelengths.

32
Q

Electron excitation phases

A

Energy is passed through the atom where the electrons in the ground state are then able to enter the excitation state, this is because the energy allows these electrons to jump energy levels as they get excited. After the energy has fully passed the electrons reach relaxation state where they emit the energy they absorbed and fall back down to their excitation state

33
Q

the light given off by atoms

A

The light given off by atoms when heated or energetically excited is emitted as a certain specific wavelength and not a continuous distribution

so hydrogen atoms when excited they give off a pinkish light

34
Q

Photoelectric effect

A

The photoelectric effect is the irradiation of a clean metal surface via radiant energy (visible light) above that of the threshold frequency value of the metal which causes the ejecting of electrons from the metal. Each metal has a different threshold frequency

35
Q

Photons:

A

Einstein stated that the visible light that irradiated the clean metal surface is a beam of particles called photons.

If these photons have a threshold frequency above that of the clean metal surface, this means they will have enough energy that they can transfer to the electrons and cause these electrons to then overcome their electrostatic attractions and eject from the atom

however, if the threshold frequency is not above that of the metals then the photons won’t have enough energy to cause the ejecting of electrons from the clean metal surface.

the work function is the amount of energy required to eject an electron

36
Q

electron ejection is affected by:

A

if the threshold frequency is above that off the clean metal surface and there is a short wavelength then electrons will be ejected from the metal

if the threshold frequency, however, is lower than that of the clean metal surface and it has a longer wavelength then electrons will not have enough energy to overcome its attractive forces and eject from the metal.

37
Q

Amplitude

A

Amplitude is known as the intensity of the wave and so the number of photons, and so if we have a great amplitude but not at the threshold frequency then no actual electrons are emitted and so we can conclude from this that the intensity and so the amplitude is irrelevant to the ejection of electrons

38
Q

Amplitude

A

Amplitudes at high intensities and high threshold frequencies will eject the most electrons

39
Q

Bohrs 3 basic principles

A
  1. Electrons in the H atom can move about the nucleus in any one of the fixed orbits
  2. the angular momentum of the electron is quantized
  3. The electron does not radiate energy as long as it remains in one of the orbits
40
Q

Problems with Bohr theory

A
  • A charged particle moving in a circular path should lose energy
  • The line spectra can’t be explained for many electrons
  • The quantum idea was artificially made
41
Q

De Broglie

A

According to de Broglie every object in motion has a wave character

42
Q

Schöndinger

A

Theorized the understanding that electrons have wavelike properties

43
Q

Heisenberg’s uncertainty principle

A

States that you cannot determine the exact location of an electron or the path it follows

44
Q

Schöndiger standing wave

A

Schöndiger associated an electron to a standing wave.
A standing wave is formed by vibrational patterns forming two waves but in opposite directions with the same frequency and amplitude

45
Q

Schöndinger

A

theorised how electrons act like standing waves as they orbit the nucleus

46
Q

wave equation

A

wave equation = wave function (orbital) squared = too the probability to find an electron in a given region of space.

47
Q

wave equation

A

the wave equation was characterised by the wave function which wave broke down into quantum numbers to predict the location of an electron

48
Q

Aufbau Principle

A

This is the building up the order of the electrons:

  1. electrons are first filled from lowest to highest energy levels
  2. no 2 electrons of the same quantum number can be in the same orbital there’s has to be at least be the difference which is the spin number - Pauli exclusion principle
  3. in degenerate orbitals electron pairing does not have until each orbital is first halve filled.
49
Q

Quantum numbers

A

S,P,D,F

50
Q

The shape of S orbitals

A

S orbitals are spherical and the probability of finding them is dependent on the distance from the nucleus and not on the direction as they don’t have planes so the orbital is a sphere

51
Q

S orbitals

A

The size of the S orbitals increase as we go higher in successive energy levels, in 2 s we have 2 circles, one inside the other with 1 region of no electron probability
in the 3 s orbital, we have 3 circles encompassing each other with w regions of no electron probability

52
Q

P orbitals

A

P orbitals have dumbell shape made up of 2 lobes and have 3 different types of orientation px,py,pz

53
Q

d orbitals

A

D orbitals are shaped as a 4 cloverleaf and have 5 different orientations to them the fifth orientation looks like a doughnut

54
Q

F orbitals

A

F orbitals are 7 and have 8 lobes maximum separated by 3 planes

55
Q

paulis exclusion principel

A

no 4 quantum numbers of the same orbital can be the same there has to be one difference which is the electron spin if the other 3 are same

56
Q

Hunds rule

A

Electron pairing in orbitals will not take place until all the orbitals are half full

57
Q

Outer electron shielding

A

The valence shell electrons are intact in the nuclear due to the effective nuclear charge acting upon it from the nucleus which is basically the attractive force of the protons on the neutrons. however, the inner electrons repel the valence electrons shielding them from the nuclear effective charge.

and so the nuclear affective charge acting on the valence shell electrons = the nuclear affective charge - the inner electron shielding

58
Q

degenerate orbitals

A

Degenerate orbitals are orbitals that are on the same energy level and the same type of orientation and so the atoms will have the same energy

for example the same types of p orbitals in the same orbital
S orbitals cannot be degenerate because of there being only one type of orientation

59
Q

Periodic properties

A
  • Atomic radius
  • Ionic radius
  • Ionization
  • Electron affinity
60
Q

Atomic radius

A

The atomic radius is the size of the atom and is determined by the number of electrons present and the nuclear effective charge

61
Q

Atomic radius property

A

As we go down the group the atomic radius increases in size this is because the Atomic number increases and so there are a greater number of electrons and so the nuclear effective charge is distributed across multiple electrons and so becomes weaker not being able to hold the electrons in so tightly

As we go across the period the atomic radius decreases in size this is because the nuclear effective charge is stranger and so held the electrons more tightly together and so decreasing the size of the atom

62
Q

Ionic radius

A

Anion - the adding of an electron to a nucleus gives the atom and overall more negative charge as there are a greater number of electrons than protons and so

63
Q

Ionic radius - anion

A

Anion - the adding of an electron to a nucleus gives the atom and overall more negative charge as there are a greater number of electrons than protons and so the atom is overall more negatively charged, due too the increase in the number of electrons this causes the ionic radius to be larger in size as there is a greater shielding effect furthermore the nuclear effective charge gets weaker making the radius larger

64
Q

Ionic radius - cation

A

Cation- the removing of an electron from a nucleus gives the atoms an overall positive charge as there are a greater number of protons than electrons and so the atom is overall positively charged and so there is a greater nuclear effective charge that holds the electrons more tightly and so decreasing the ionic radius size and so having smaller radius’s

65
Q

Diamagnetism

A

Diamagnetism is solids with no unpaired electrons and so in the presence of a magnetic filed they show repulsion

66
Q

Paramagnetism

A

Paramagnetism is solid with unpaired electrons and so in the presence of a magnetic filed they show attraction

Chemistry BMC ESE (2 decks)

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