Atoms, Bonds and Groups

Definitions for the Atoms, Bonds and Groups paper for OCR Chemistry A.

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  • Created on: 21-05-14 13:39
Atom
Positively charged nucleus containing most of the mass, surrounded by atomic shells with orbiting electrons of negative charge and negligible mass.
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Atomic Number
Defines the element. Shows the number of protons in the nucleus (and number of electrons).
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Mass Number
- Mass of the atom: number of protons + number of neutrons.
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Isotope
Atom with same number of protons but different number of neutrons.
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Relative Atomic Mass
Average weighted mass of an atom compared with 1/12th of the mass of an atom of carbon-12.
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Relative Isotopic Mass
Mass of an atom of an isotope compared with 1/12th of the mass of an atom of carbon-12.
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Amount of Substance
Number of Atoms - mol
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Avagadro's Contant
Number of particles per mole = 6.02 x 10^23 mol^-1
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Molar Mass
Mass per mole of a substance - gmol^-1
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Periodicity
Patterns repeated across different periods on the Periodic Table.
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Emperical Formula
The simplest whole number ratio of atoms of each element present in a compound.
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Molecular Formula
The actual number number of atoms of each element in a molecule.
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Concentration
The amount of solute (in mol) per 1dm^3 of solution - moldm^3
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Acids
Proton donors - when in water (aqueous solution) they release H+ ions.
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Bases
Proton acceptors - take H+ ions and neutralise acids.
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Alkalis
Solubles bases which release OH- ions
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Salts
Produced when H+ ion is replaced by a metal ion or NH4+
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Anhydrous
Substance containing no water molecules.
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Hydrated
Crystalline compound containing water molecules.
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Water of Crystallistion
Water molecules that form part of the crystalline structure of a (hydrated) compound.
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Reduction
Gain of electrons.
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Oxidation
Loss of electrons.
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Redox
A reaction in which species are reduced and oxidised.
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Disproportionation Reaction
A reaction in which the same species is both reduced and oxidised.
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First Ionisation Energy
The energy required to remove one electron from the outer shell from one mole of gaseous atoms to form one mole of gaseous atoms to form one mole of gaseous 1+ ions.
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Second Ionisation Energy
The energy required to remove one electron from the outer shell from one mole of gaseous 1+ ions to form gaseous 2+ ions.
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Nuclear Charge
The attraction from the protons in the nucleus with electrons.
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Electron Shielding
The repulsion between electrons in different inner shells which reduce the net attractive force form the positive nucleus on the outer shell electrons.
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Atomic Radius
The distance from the outer shell of electrons to the nucleus of the atom. Increases down a group but decreases across a period.
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Orbital
A region that can hold up to two electrons of opposite spins.
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Subshell
The space an electron can occupy within each shell.
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Ionic Bonding
Electrostatic attraction between oppositely charged ions.
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Covalent Bonding
Bond formed by a shared pair of electrons.
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Dative/Coordinate Bonding
Bond formed when one bonding atom gives both of its electrons from a pair.
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Bonding Pairs
Number of pairs of electrons in a bond.
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Lone Pars
Number of pairs of electrons that aren't part of a bond.
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Bond Angle
Angle between bonds in a molecule which are defined by the number of bonding pairs and lone pairs of electrons. Electron pairs repel each other and space out evenly. Lone pairs repel more than bonding pairs.q
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Intermolecular Forces (IMF)
Forces of attraction between molecules.
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Electronegativity
The ability of an atom to attract the bonding electrons in a covalent bond. Creates permanent dipoles (polar).
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Dipole-Dipole Interactions
IMF. Molecules with permanent dipoles allow for weak intermolecular bonds to be formed between the molecules.
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Van der Waals
IMF. Formed when the movement of electrons unbalances the distribution of the charge in shells. Causes instantaneous dipole which attracts/repels electrons in neighbouring molecules. Dipoles formed by instantaneous dipoles are 'induced dipoles'.
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Hydrogen Bond
Strong dipole-dipole interaction between H atom (electron deficient) and lone pair of electrons on highly electronegative atom (e.g. O or N)
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Metallic Bonding
The attraction of positive ions to delocalised electrons.
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Giant Ionic Lattice
Formed by the attraction of oppositely charged ions. Each ion is surrounded bu the oppositely charged ions and the ions attract each other to form a lattice.
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Giant Covalent Lattice
Three dimensional structure of atoms bonded together by strong IMFs.
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Simple Molecular
Three dimensional structure of molecules bonded together by weak IMFs - e.g. VdWs.
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Other cards in this set

Card 2

Front

Defines the element. Shows the number of protons in the nucleus (and number of electrons).

Back

Atomic Number

Card 3

Front

- Mass of the atom: number of protons + number of neutrons.

Back

Preview of the back of card 3

Card 4

Front

Atom with same number of protons but different number of neutrons.

Back

Preview of the back of card 4

Card 5

Front

Average weighted mass of an atom compared with 1/12th of the mass of an atom of carbon-12.

Back

Preview of the back of card 5
View more cards

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