CHEMISTRY KEY DEFINTIONS_UNIT ONE (FINAL)

Key Defintions for Unit One of the Course

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Unit One-Atoms Bonds and Groups
Module One- Atoms and Reactions
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2. Atomic Structure
2. Atomic Structure
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Isotopes
Atoms of the same element with different number of neutrons.
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Atomic (Proton) Number
The number of protons in the nucleus of an atom.
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Mass (Nucleon) Number
The number of particles (protons+neutrons) in the nucleus.
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Ion
A positively or negatively charged atom or (covalently bonded) group of atoms(a molecular ion)
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3. Atomic Masses
3. Atomic Masses
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Realtive Isotopic Mass
The mass of an atom of an isotope compared with one-twelfth of the mass of an atom of carbon-12
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Relative Atomic Mass, Ar
The weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12
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Relative Molecular Mass, Mr
The weighted mean mass of a molecule compared with one-twelfth of the mass of an atom of caron-12
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Relative Formula Mass
The weighted mean mass of a formula unit compared with one-twelfth of the mass of an atom of carbon-12
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4. Amount of Substance
4. Amount of Substance
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Amount of Substance
The quantity whose unit is the mole. Chemists use 'amount of substance' as a means of counting atoms.
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Avogadro Constant, NA
The number of atoms per mole of the carbon-12 isotope (6.02 x 10 23 mol-1)
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Mole
The amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the carbon-12 isotope.
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Molar Mass, Mr
The mass per mole of a substance. The units of molar mass are gmol-1
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5. Types of Formula
5. Types of Formula
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Emprical Formula
The simplest whole number ratio of atoms of each element present in a compound
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Molecule
A small group of atoms held together by covalent bonds
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Molecular Formula
The actual number of atoms of each element present in a molecule
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6. Moles and Gas Volumes
6. Moles and Gas Volumes
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Molar Volume
The volume per mole of gas. The units of molar volume are dm3mol-1. At room temperature and pressure the molar volume is approximately 24.0dm3 mol-1
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7. Moles and Solutions
7.Moles and Solutions
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Concentration
The amount of solute, in mol, dissolved per 1dm3 (1000 cm3) of solution
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Standard Solution
A solution of a known concentration. These are usually used in titrations to determine unknown information about another substance.
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8. Chemical Equations
8. Chemical Equations
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Species
Any type of particle that takes part in a chemical reaction.
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9. Moles and Reactions
9. Moles and Reactions
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Stoichiometry
The molar relationship between the relative quantitites of sunstances taking part in a reaction
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10. Acids and Bases
10. Acids and Bases
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Acid
A species that is a proton donor.
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Base
A species that is a proton acceptor
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Alkali
A type of base that dissolves in water forming hydroxide ions. OH-(aq) ions.
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11. Salts
11. Salts
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Salt
Any chemical compound formed from an acid when a H+ ion from the acid has been replaced by a metal ion, or another positive ion, such as the ammonium ion NH4+
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Cation
Positively charged ion
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Anion
A negatively charged ion
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12. Water of Crystallisation
12. Water of Crystallisation
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Hydrated
Refers to a crystalline compound containing water molecules
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Anhyrdous
A substance that contains no water molecules
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Water of Crystallisation
Water molecules that form an essential part of the crystalline structure of a compound.
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14. Oxidation Number
14. Oxidation Number
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Oxidation Number
A measure of the number of electrons that an atom uses to bond with atoms of another element; they are derivied from a set of rules.
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15. Redox Reactions
15. Redox Reactions
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Oxidation
The loss of electrons or an increase in oxidation number.
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Reduction
The gain of electrons or a decrease in oxidation number.
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OILRIG
Oxidation Is Loss Reduction Is Gain
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Redox Reaction
Reaction in which both reduction and oxidation take place.
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Reducing Agent
Reagent that reduces (adds electrons to) another species.
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Oxidising Agent
Reagent that oxidises (takes electrons from) another species
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Unit One-Atoms, Bonds and Groups
Module 2- Electrons, Bonding and Structure
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1. Evidence for Shells
1. Evidence for Shells
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First Ionisation Energy
The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.
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Electron Shielding
The repulsion between electrons in different inner shells. Shielding reduces the net attractive force from the nucleus on the outer shell electrons.
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Successive Ionisation Energies
Measure of the energy required to remove each electron in turn.
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2. Shells and Orbitals
2. Shells and Orbitals
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Shell
Group of atomic orbitals with the same principal quantum number,n. Also known as main energy level.
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Prinicipal Quantum Number,n.
Number representing the relative overall energy of each orbital, which increases with distanced from the nucleus. The sets of orbitals with the same n value are referred to as electron shells or energy levels
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Atomic Orbital
A region within an atom that can hold up to two electrons with opposite spins
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3.Sub-shells and Energy Levels
3. Sub-Shells and Energy Levels
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Sub-Shell
A group of the same type of atomic orbitals (s, p, d and f) within a shell.
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Electron Configuration
The arrangement of electrons in an atom.
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5. An Introduction to Chemical Bonding
5. An Introduction to Chemical Bonding
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Compound
A substance formed from two or more chemically bonded elements in a fixed ratio, usually shown by a chemical formula
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6. Ionic Bonding
6. Ionic Bonding
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Ionic Bond
The electrostatic attraction between oppositely charged ions.
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Giant Ionic Lattice
A three dimensional structure of oppositely charged ions, held together by strong ionic bonds.
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7. Ions and the Periodic Table
7. Ions and the Periodic Table
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Group
A vertical column in the periodic table. Elements in the same group have similar chemical properties and their atoms have the same number of outer shell electrons.
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8. Covalent Bonding
8. Covalent Bonding
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Covalent Bond
A bond formed by a shared pair of electrons.
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Lone Pair
An outer-shell pair of electrons that is not involved in chemical bonding.
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9.Further Covalent Bonding
9. Further Covalent Bonding
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Dative Covalent/Coordinate Bond
A shared pair of electrons which has been provided by one of the bonding atoms only.
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11. Electronegativity and Polarity
11. Electronegativity and Polarity
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Electronegativity
A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond
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Permanent Dipole
A small charge difference across a bond that results from a difference in the electronegativities of the bonded atoms
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Polar Covalent Bond
Has a permanant dipole.
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Polar Molecule
Has an overall dipole when you take into account any dipoles across the bonds.
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12. Intermolecular Forces
12.Intermolecular Forces
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Intermolecular Force
An attractive force between neighboring
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Permanent Dipole-Dipole Force
A weak attractive force between permanent dipoles in neighboring polar molecules.
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Van der Waals Forces
Attractive forces between induced dipoles in neighboring molecules.
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13. Hydrogen Bonding
13. Hydrogen Bonding
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Hydrogen Bond
A strong dipole-dipole attraction between: an electron deficient hydrogen atom on one molecule and a lone pair of electrons on a highly electronegative atom on a different molecule
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14. Metallic Bonding and Structure
14. Metallic Bonding and Structure
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Metallic Bonding
The electrostatic attraction between positive metal ions and delocalised electrons.
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Delocalised Electrons
Shared between more than two atoms
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Giant Metallic Lattice
Three-dimensional structure of postive ions and delocalised electrons, bonded together by strong metallic bonds.
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16.Structures of Covalent Compounds
16.Strutures of Covalent Compounds
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Simple Molecular Lattice
Three dimensional structure of molecules,bonded together by weak intermolecular forces
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Giant Covalent Lattice
Three dimensional structure of atoms, bonded together by strong covalent bonds
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Unit One: Atoms, Bonds and Groups
Module Three: The Periodic Table
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3. The Modern Periodic Table
3. The Modern Periodic Table
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Period
A horizontal row of elements in the Periodic Table.Elements show trends in properties across a period.
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Group
A vertical column in the Periodic Table. Elements in a group have similar chemical properties and their atoms have the same number of outer shell electrons.
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Periodicity
A regular periodic variation of properties of elements with atomic number and position in the Periodic Table
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7. Group 2 Compounds: Reactions
7. Group 2 Compounds: Reactions
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Thermal Decomposition
The breaking up of a chemical substance with heat into at least two substances
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8. Group 7 Elements: Redox Reactions
8. Group 7 Elements: Redox Reactions
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Displacement Reaction
A reaction in which a more-reactive element displaces a less reactive element from an aqueous solution of the latters ions.
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Disproportionation
The oxidation and reduction of the same element in a redox reaction
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9. Group 7 Elements: Uses and Halide Tests
9. Group 7 Elements: Uses and Halide Tests
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Precipitation Reaction
The formation of a sold from solution during a chemical reaction. Precipitates are often formed when two aqueous solutions are mixed together
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Card 2

Front

2. Atomic Structure

Back

2. Atomic Structure

Card 3

Front

Atoms of the same element with different number of neutrons.

Back

Preview of the back of card 3

Card 4

Front

The number of protons in the nucleus of an atom.

Back

Preview of the back of card 4

Card 5

Front

The number of particles (protons+neutrons) in the nucleus.

Back

Preview of the back of card 5
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