Thermochemistry Definitions Flashcards
(54 cards)
1
Q
Atomic structure
A
- All matter is made up of tiny particles called atoms (no charge).
- Atoms are made up of subatomic particles called protons (positively charged), and neutrons (neutral), and electrons (negatively charged).
- Protons and neutrons are found in the atoms nucleus (centre).
- 99.9% of the atoms mass is in the nucleus.
- The electrons move rapidly around the nucleus in shells (different energy levels) within the atom.
2
Q
Define Enthalpy
A
Heat energy
3
Q
Define Electron Configuration
A
The arrangement of electrons in the energy levels (shells) around the nucleus.
4
Q
Define Nucleus
A
A spherical dense, positively charged core of an atom, made up of protons and neutrons.
5
Q
Define Covalent bonding
A
Valence electrons are shared between two non-metal atoms, (shared electrons).
6
Q
Define Ionic bonding
A
Valence electrons transferred from metal to non-metal atoms to form positive and negative ions. Oppositely charged ions are attracted to each other/like charged ions repel each other.
7
Q
Define Octet rule
A
8 electrons for stability
8
Q
Define Nuclei
A
Plural for nucleus
9
Q
Define Polar covalent bond
A
uneven/unequal sharing of electrons
10
Q
Define Non polar covalent bond
A
An even/equal sharing of electrons
11
Q
Define Coordinate covalent bond
A
A covalent bond in which both electrons come from the same atom.
12
Q
Define Anion
A
Negatively charged ion
13
Q
Define Cation
A
Positively charged ion
14
Q
Atomic Number (z)
A
Number of protons
15
Q
Define Ionic formula
A
The ratio of positive to negative ions present within the ionic compound.
16
Q
Define Molecule
A
Two or more atoms chemically bonded to form a single compound.
17
Q
Define Electrostatic attraction
A
Attraction between a positive and negative force.
18
Q
Define Delocalised Electron
A
An electron that doesn’t live in one atom or shell.
19
Q
Mass Number (A)
A
Total number of protons and neutrons
20
Q
Define Ion
A
A charged particle that has gained or lost electrons.
21
Q
Define Shared electrons
A
An electron belonging to another atoms nucleus
22
Q
Calculating the number of neutrons
A
mass number - number or protons
23
Q
Define Metallic bonding
A
Valence electrons become delocalised and form a sea of free electrons which attracts positive metal ions.
24
Q
Define S,P,F,S,P
A
- Solid
- Particles
- forces
- strength
- property
25
Define Aqueous
Chemical has been dissolved in water
26
Define Intramolecular
Forces WITHIN the molecule that keep the molecule together
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Define Intermolecular
The forces BETWEEN molecules
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Define Solvent
Able to dissolve other substances
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Define Solute
Substance being dissolved
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Define Ductile
Material able to be stretch, pulled into thin wire without breaking
31
Define Covalent Network
Atoms covalently bonded together into a three dimensional network or layers of two-dimensional networks.
32
Define Electronegativity
A measure of how strongly bonded electrons are attracted to the nucleus of an atom in a bond. The most electronegative elements are FONCL. Electronegativity (En) increases up a group and along a period.
33
Define Electron density
Electron density is the number of bonds and unpaired electrons around an atom. Double and triple bonds count as one region of electron density.
34
Define VSEPR
Valence shell electron pair repulsion: when electron pairs in the valence shell arrange themselves to have the maximum distance between negatively charged electrons. This rule helps us determine the shape of the molecule.
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Define Ionization
Any process by which electrically neutral atoms or molecules are converted to electrically charged atoms or molecules (ions) through gaining or losing electrons.
36
Define Dipole (δ)
A dipole is a molecule or part of a molecule that has both a positive and negative end due to an uneven distribution of electrons. Its like a tiny magnet with two opposite charges.
37
Define Bond dipole
A separation of electric charge within a chemical bond, where one atoms has a slightly negative charge. This happens when atoms in a molecule have different electronegative's, causing electrons to be pulled closer to one atom than the other, creating a polar bond.
38
Define Dipole moment
A dipole moment is a measure of the separation of positive and negative electrical charges within a molecule. It indicates how polar a molecule is. The greater the difference in electronegativity between atoms and the more asymmetric the molecular shape, the larger the dipole moment.
Here’s what influences dipole moments:
Electronegativity Difference: A large difference in electronegativity between atoms (like in the C–F bond in Freon-11) creates a partial charge separation, where one atom pulls electrons more strongly.
Molecular Geometry: Even if a molecule contains polar bonds, the overall dipole moment depends on its geometry. If the shape is symmetrical, the dipoles can cancel out. In the case of Freon-11, the geometry is not perfectly symmetrical, leading to an overall dipole moment.
39
Define FONCL
F= Fluorine
O= Oxygen
N= Nitrogen
Cl= Chlorine
(most electronegative elements, Fluorine being the most!)
40
Define the term standard
conditions
A standard-state condition refers to the conditions under which thermodynamic measurements are made.
Temperature: 25 degrees Celsius (298.15 degrees Kelvin) Pressure: 1 atm (atmosphere)= 101.325 kPa
41
Define enthalpy of
formation (ΔfH°)
The standard enthalpy of formation is a measure of the energy released or consumed when one mole of a substance is created from elements in their standard states. The standard states are the form you would find an element in at 1 bar pressure and 25 °C.
42
Define enthalpy of
combustion (ΔcH°)
The enthalpy of combustion of a substance is defined as the heat energy given out when one mole of a substance burns completely in oxygen. Combustion reactions are exothermic so the value for the enthalpy change (ΔH) is always negative.
43
Define enthalpy of
vaporisation (ΔvapH°)
The enthalpy of vaporization, also known as the heat of vaporization or heat of evaporation, is the amount of energy (enthalpy) that must be added to a liquid substance to transform a quantity of that substance into a gas.
44
Define enthalpy
of fusion (ΔfusH°)
The enthalpy of fusion is the amount of energy required to convert one mole of solid into liquid.
45
Define enthalpy of
sublimation (ΔsubH°)
The heat required to sublimate (change from solid to gas) one mole of a substance at a given combination of temperature and pressure, usually standard temperature and pressure (STP).
46
Define the term heat
capacity
Heat capacity or thermal capacity is a physical property of matter, defined as the amount of heat to be supplied to an object to produce a unit change in its temperature. The SI unit of heat capacity is joule per kelvin.
47
Define entropy
A measure of randomness or disorder of a system. A very regular, highly ordered system (diamond, for example) will have a very low entropy. A very disordered system (a mixture of gases at a high temperature, for example) will have a high entropy. But a system becomes more stable when its energy is spread out in a more disordered state.
Suppose you managed to arrange some gaseous molecules in a container and then you let them go. Each collision between two molecules will cause them to change direction, and it will probably speed up one of them, and slow down the other. After a very short time, their arrangement in space will be chaotic, and so will the way energy is shared between them. The faster moving particles have more energy; the slower ones less. The entropy has increased in terms of the more random distribution of the energy.
48
Define first ionisation energy
By definition, the first ionisation energy of an element is the energy needed to remove the outermost, or highest energy, electron from a neutral atom in the gas phase.
49
Define isoelectronic
Atoms and ions that have the same electron configuration.
50
Define RAM
Relative Atomic Mass
51
Define NA percentage meaning on an isotope?
In physics, natural abundance (NA) refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass (a weighted average, weighted by mole-fraction abundance figures) of these isotopes is the atomic weight listed for the element in the periodic table.
52
Define electron orbitals
Orbitals are regions where electrons are most likely to be found at any one time.
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Nuclear Charge
- Effective nuclear charge is used to explain the trends in physical and chemical properties of elements.
- Nuclear charge is given by the atoms atomic number and simply increases by one between successive atoms as a proton is added to the nucleus.
-However, the valence electrons determine many of the properties and are shielded (repelled) from the nucleus by the inner electrons. This reduces the attraction between the valence electrons and the nucleus.
- The effective nuclear charge experienced by the valence electrons is reduced (less the the full nuclear charge).
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