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Chemistry > Unit 1 > Flashcards

Unit 1 Flashcards

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1
Q

The oxidation number of an uncombined element is…

A

Zero

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2
Q

The sum of oxidation numbers in an ion or compound is…

A

Equal to the overall charge

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3
Q

The oxidation number of Oxygen is -2 in compounds except with…

A

Fluorine, peroxides or superoxides

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4
Q

The oxidation number of hydrogen is +1 in compounds except in…

A

Metal hydrides

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5
Q

If the oxidation number increases during a reaction, the species has been…

A

Oxidised

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6
Q

If the oxidation number decreases during a reaction, the species has been…

A

Reduced

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7
Q

What happens to the atomic and mass number of an atom when it emits an alpha particle?

A

Mass number decreases by 4
Atomic number decreases by 2

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8
Q

What happens to the atomic and mass number of an atom when it emits a beta particle?

A

Mass number unchanged
Atomic number increases by 1

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9
Q

What happens to the atomic and mass number of an atom when it undergoes electron capture?

A

Mass number unchanged
Atomic number decreases by 1

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10
Q

What happens to the atomic and mass number of an atom when it emits a positron?

A

Mass number unchanged
Atomic number decreases by 1

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11
Q

Define Half life

A

The time taken for the radioactivity of a radioisotope to decrease by half.

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12
Q

Draw an S orbital.

A

Circle

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13
Q

Draw a P orbital.

A

Figure 8 on x, y or z axis

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14
Q

what are the three rules when filling shells and orbitals with electrons?

A

Otters Properly Tan

(in Order) Electrons fill atomic orbitals in order of increasing energy - Aufbau

(Parallel) The orbitals will first fill with one electron each with parallel spins before a second electron is added with the paired spin - Hund

(Two) A maximum of two electrons can occupy any orbital each with opposite spins - Pauli

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15
Q

What are the three main factors that affect ionisation energy?

A

DEN

Distance of the outer electrons to the nucleus

Electron shielding

Size of the positive Nuclear charge

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16
Q

Why do successive ionisation energies always increase? (3)

A

NErD

Greater effective nuclear charge as the same number of protons are holding fewer and fewer electrons

As each electron is removed, these is less and less electron-electron repulsion and each shell will be drawn in slightly closer to the nucleus

As the distance of each electron from the nucleus decreases, nuclear attraction increases.

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17
Q

from smallest to largest wavelength, electromagnetic spectrum.

A

Greg’s
Xylophone
Ultimately
Vanished
Into
Micro
Remains

Gamma ray
X-ray
Ultra-Violet
Visible
Infra-red
Microwaves
Radio waves

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18
Q

What wavelengths does the visible light spectrum include…

A

(400 - 700)nm

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19
Q

Explain absorption spectra.

A

White light is passed through the vapour of an element. Certain wavelengths are absorbed by the atom and therefore removed from the light. The wavelengths are equal to the energy required for the atom to promote lower energy electrons to higher energy levels. Black lines appear on the spectra.

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20
Q

Explain emission spectra

A

An atom is given energy by heating or electric field. Electrons are excited and the energy promotes them from lower to higher energy levels. When the source energy is removed, the electrons leave the excited state and fall back to the lower energy level. The energy lost is released as a photon of certain frequency. The coloured lines match the frequency of visible light emitted by the photon.

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21
Q

Equation for energy of a wave is…

A

E = hc/λ

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22
Q

What are the three series of light and which electromagnetic region do they correspond to?

A

Lyman - Ultraviolet (LUndon)
Balmer - Visible (BVarian slice)
Paschen - Infra-red (PIe face)

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23
Q

What is the convergence limit?

A

When the spectral lines become so close that they have a continuous band and lines can not be destinguished.

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24
Q

What are the two equations that make up:
E = hc/λ

A

E = hf
c = fλ

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25
What stops Alpha radiation?
Thin sheet of paper.
26
What stops Beta Radiation?
Thin sheet of Aluminium
27
What stops Gamma Radiation?
Lead or concrete.
28
What are the consequences of radiation to living cells?
Ionising radiation can cause mutations and form cancerous cells.
29
Which radiation is most harmful if ingested?
Alpha - It is bigger so unable to escape the body and it is highly ionising so very likely to cause mutations.
30
Which Radiation is most harmful outside of the body?
Gamma - It is the smallest so able to enter the body and cause mutations to living cells.
31
What are the beneficial uses of radiation in medicine?
Colbalt-60 - Radiotherapy treatment of cancer.
32
Explain Carbon Dating.
All living organisms absorb carbon including some radioactive carbon-14. When the organism dies, no more absorption occurs but that which is present decays. The rate of decay decreases over time so the activity can be used to calculate the age of an organism.
33
Explain Potassium-Argon Dating.
Used to estimate the geological age of rocks. Potassium-40 can decay to argon-40 by the nucleus gaining an inner electron. Measuring the ratio of potassium-40 to Argon-40 in a rock gives an estimate of its age.
34
What are the benefits of radiation in Industry and analysis?
Dilution analysis - Finding the mass of a substance in a mixture. Measuring the thickness of metal strips of foil.
35
What are the 4 stages of the Mass Spectrometer?
Ionisation Acceleration Deflection Detection
36
What happens in the Ionisation section of a mass spectrometer?
A vaporised sample is passed into the chamber. The sample is bombarded with electrons, some collisions will be strong enough to knock electrons out of the particles. Most ions will be 1+ as it is much more difficult to knock electrons out of an already positive particle.
37
What happens in the acceleration section of a mass spectrometer?
An electric field accelerated the positive ions to high speed.
38
What happens in the deflection section of a mass spectrometer?
Different ions are deflected by the magnetic field by different amounts, depending on: Their Mass Their Charge These two factors are combined into the mass/charge ratio.
39
What happens in the Detection section of a mass spectrometer?
The ions passing through the machine are detected electrically. Only ions with correct mass /charge ratio make it through to the ion detector. The signal is then amplified and recorded.
40
What is a molecular ion?
A positive ion formed in a mass spectrometer from the whole molecule.
41
What is fragmentation?
The splitting of molecules into smaller parts in a mass spectrometer.
42
Define a mole.
The amount of a substance which contains the same number of particles as there are atoms in exactly 12g of carbon-12.
43
Define Mr.
The mass of a compound relative to one-twelfth the mass of a carbon-12 atom.
44
Define Molar Mass.
Mass of one mole of a substance in grams per mole (g/mol).
45
How do you calculate empirical formula?
( % / Mr ) of each Divide all by smallest number
46
All Mole calculation equations
m = n Mr n = c v n = N / Na n = V / Molar gas volume at temp
47
What is the Ideal gas equation and what does each letter represent?
pV = nRT p = Pressure V = Volume n = Moles R = 8.31 - gas constant T = Temperature
48
Atom economy equation.
mass or Mr of required product / total mass or Mr of reactants x100
49
Percentage yield.
Theoretical mass / actual mass produced x100
50
What is an ionic bond?
A bond formed by the electrical attraction between positive and negative ions.
51
What is a covalent bond?
A pair of electrons with opposed spins shared between two atoms with each atom giving one electron.
52
What is a coordinate bond?
A pair of electrons with opposed spins shared between two atoms with both electrons coming from the same atom.
53
What is electronegativity?
A measure of the electron-attracting power of an atom in a covalent bond.
54
What is the electronegativity different of a non polar, covalent bond?
<0.4
55
What is the electronegativity difference in a polar, covalent bond?
0.4< <1.9
56
What is the electronegativity difference in an ionic bond?
>2.0
57
What are intermolecular forces? + 3 types
The weak forces between molecules Dipole - Dipole Induced dipole - Induced dipole Hydrogen bonding
58
What do the intermolecular forces determine in a substance?
Physical properties
59
What are intramolecular forces?
Strong bonds between atoms in a molecule. e.g. covalent
60
What are van der Waals forces?
Dipole - Dipole and Induced Dipole - Induced Dipole forces.
61
Explain Dipole - Dipole Forces.
62
Explain Induced Dipole - Induced Dipole Forces
63
Explain Hydrogen Bonding.
Occur between molecules which contain a hydrogen atom boded to a very electronegative atom i.e. Fluorine, Oxygen or Nitrogen. Because of the large difference in electronegativity and size of the two atoms, the δ+ on the hydrogen has a high charge density which attracts a a lone pair of electrons in the electronegative atom in another molecule. The hydrogen atom becomes sandwiched between two electronegative atoms; Covalently bonded to one and hydrogen-bonded to the other.
64
What is the effect of hydrogen bonding on Boiling temperature?
Very strong intermolecular forces so increase the boiling point.
65
What is the effect of hydrogen bonding on solubility in water?
The most significant intermolecular forces between water molecules are hydrogen bonds. Covalent compounds that can replace these by forming new hydrogen bonds with water will dissolve.
66
What are the three points of 'Valence Shell Electron Pair Repulsion Theory'?
1. The shape of a molecule is determined by the number pairs of electrons in the valence shell of the central atom. 2. The electron pairs arrange themselves around the central atom such that they are as far apart as possible so that the repulsion is at its minimum. 3. lone pair - lone pair repulsion > lone pair - bonding pair repulsion > bonding pair - Bonding pair repulsion.
67
Number of bonding/lone pairs and bond angle in a linear molecule.
Two bonding pairs around a central atom. 180°
68
Number of bonding/lone pairs and bond angle in a trigonal planar molecule.
Three bonding pairs around a central atom. 120°
69
Number of bonding/lone pairs and bond angle in a tetrahedral molecule.
Four electron pairs around a central atom. 109.5°
70
Number of bonding/lone pairs and bond angle in a trigonal pyramidal molecule.
Three bonding pairs, one lone pair 107°
71
Number of bonding/lone pairs and bond angle in a bent molecule.
Two bonding pairs, two lone pairs 104.5°
72
Number of bonding/lone pairs and bond angle in a trigonal bipyramidal molecule.
Five bonding pairs around a central atom. 90° and 120°
73
Number of bonding/lone pairs and bond angle in a octahedral molecule.
Six bonding pairs around a central atom 90°
74
What is the trend in ionisation energy in the periodic table? Explain
General increase across a period - increase in nuclear charge but electrons at the same energy level so little increase in shielding. Decrease from group 2 to 3 - group 3 outer electron is in s new subshell of slightly higher energy level so there is some shielding. Decrease from group 5 to 6 - in group 6, the electron is removed from an orbital containing a pair of electrons, the repulsion between the two electrons makes it slightly easier to remove. Decreases down a group - outer electron has increased shielding as it is further away from the nucleus. This outweighs the increase in nuclear charge.
75
What is the trend in electronegativity in the periodic table? Explain
Increases across a period - increase in nuclear charge but same shielding so greater attraction to bonding pair. Decreases down a group - bonding electrons have increased shielding from the nucleus so attraction decreases. Most electronegative are top right of the periodic table: N, O, F
76
What is the trend in Melting/Boiling points in the periodic table? Explain
Follows the change in structure and bonding throughout the groups. (Groups 1-3 generally) Metalic - Increase across periodic table as the charge increases and there are more electrons per metal ion. (Group 4 generally) Giant covalent - Very strong covalent bonds between each atom require large amount of energy to overcome. (Groups 5-7 generally) simple molecular - intramolecular covalent bonds are strong but intermolecular bonds are weaker and do not require a lot of energy to break. (Group 0 generally) These have the lowest melting temperatures as they exist as atoms and are only held together by induced dipole - induced dipole forces.
77
OIL RIG
Oxidation is Loss Reduction is Gain
78
Reaction of group 1 metals with water.
React vigorously with water to form the hydroxide and hydrogen. (increases down the group) Lithium - floats on water, gently fizzing Sodium - melts into ball that dashes around the surface Potassium - melts into ball and catches fire Caesium - explodes and shatters the glass container.
79
Reactions of group 2 metals with water.
React less vigorously than group 1 metals. Still hydroxide and hydrogen are formed. (increases down the group) Magnesium - reacts with steam to produce hydroxide and vapour. Calcium - produces steady stream of bubbles, liquid goes cloudy as white ppt of calcium hydroxide forms. Barium - greater effervescence and solution is clearer as barium hydroxide is more soluble.
80
Trends in reactivity in the S-Block.
Reactivity increases down the groups as they need to loose an electron to form their positive ions. Ionisation energy decreases down a group so less energy is required for the elements to loose an electron and react further down the group.

Chemistry (3 decks)

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