Karteikarten
Chemistry revision F321
Karten in diesem Stapel (49)
- 1Atomic numberThe number of protons in the nucleus of an atom.
- 2Mass numberThe number of protons and neutrons in the nucleus of an atom.
- 3IsotopesAtoms of the same element with different numbers of neutrons.
- 4Why do isotopes have similar chemical properties?They have the same number of electrons in their outer shell.
- 5Relative isotopic massThe mass of an isotope compared to 1/12th of the mass of one atom of carbon 12.
- 6Relative atomic massThe weighted mean mass of an atom compared to 1/12th of one atom of carbon 12.
- 7ProtonsRelative mass: 1
Relative charge: +1
Position in the atom: Nucleus - 8NeutronsRelative mass: 1
Relative charge: 0
Position in the atom: Nucleus - 9ElectronsRelative mass: 1/2000
Relative charge: -1
Position in the atom: Shells - 10Relative Molecular massThe weighted mean mass of a molecule relative to 1/12 of one atom of carbon 12.
- 11OrbitalA volume of space that can hold up to two electrons with opposite spins.
- 12Order of the orbitals1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
(max 36 electrons) - 13First ionisation energyThe amount of energy required to remove one electron from each atom in one mole of gaseous atoms (to form one mole of positive gaseous ions.)
- 14Successive ionisation energiesSecond ionisation energy:
O+ (g) ----> 0 2+ (g) + e-
Third ionisation energy:
O 2+ (g) ----> O 3+ (g) + e- - 15Trend in successive ionisation energiesRemoval of additional electrons results in an increase in ionisation energy because:
Same number of protons are now attracting fewer electrons in the ion
One less electron means there is less electron-electron repulsion
The O+ ion is smaller than the O atom, therefore the next electron to be removed will be closer to the nucleus
Next electron will experience greater nuclear attraction. - 16CARS: across a periodIncrease in ionisation energy:
C inc - less electrons added to same no. of protons
A inc
R dec - extra electron shell added
S eq - electrons added to same shell - 17CARS - down a groupIonisation energy decreases:
C inc - outweighed by radius and shielding
A dec
R inc - extra electron shell added
S - more electron-electron repulsion - 18Acid + Metal ---> 2HCl (aq) + Mg (s) --->Salt + hydrogen gas
MgCl2 (aq) + H2 (g) - 19Acid + Metal Oxide ---> 2HCl (aq) + CaO (s) --->Salt + Water
CaCl2 (aq) + H20 (l) - 20Acid + Metal hydroxide ---> HNO3 (aq) + NaOH (s) --->Salt + Water
NaNO3 (aq) + H20 (l) - 21Acid + Metal carbonate ---> H2SO4 (aq) + CaCO3 (s) --->Salt + Water + Carbon dioxide
CaSO4 (aq) + H2O (l) + CO2 (g) - 22Ionic bondThe electrostatic force of attraction between oppositely charged ions (occurs between a metal and a non metal.)
- 23Covalent bondA shared pair of electrons (occurs between two non metals.)
- 24Dative covalent bondA shared pair of electrons, both of which come from the same atom. E.g. NH4+ formed by reaction of NH3 + H+.
- 25Metallic bondThe electrostatic force of attraction between positive metal ions and delocalised electrons.
- 26Exceptions of the octet ruleWhen there are not enough electrons to complete the octet. E.g. Be & B in period 2 when they are the central atom.
- 27Expansion of the octet ruleWhen each atom has more than 8 electrons. E.g. Groups 5-7 from period 3 downwards when they are the central atom.
- 28Linear shaped moleculesE.g. Becl2 BeH2 CO2
2 bonded pairs
0 lone pairs
180° bond angles - 29Trigonal planar shaped moleculesE.g. BF3 BCl3 BBr3 SO3
3 bonded pairs
0 lone pairs
120° bond angles - 30Tetrahedral shaped moleculesE.g. CH4 SiH4 NH4+ CCl4
4 bonded pairs
0 lone pairs
109.5° bond angles - 31Octahedral shaped moleculesE.g. SF6 SeF6
6 bonded pairs
0 lone pairs
90° bond angles - 32Pyramidal shaped moleculesE.g. NH3 NCl3 PCl3
3 bonded pairs
1 lone pair
107° bond angles (-2 . 5° for each lone pair) - 33Non-linear shaped moleculesE.g. H2O H2S
2 bonded pairs
2 lone pairs
104.5° bond angles - 34ElectronegativityThe ability of an atom to attract a pair of electrons in a covalent bond towards itself.
- 35Pauling scaleElectronegativity increases to the top right of the periodic table, with F being the most electronegative.
- 36Permanent dipoleA difference in electronegativity between 2 atoms results in a small charge difference. Eg. HCl H △+ Cl△- electrons always closer to Cl atom.
- 37Polar bonds in a non polar moleculeA molecule may have polar covalent bonds because the molecules are symmetrical. The dipoles act in opposite directions and cancel each other out.
- 38Permanent dipole-dipole forcesOne molecule can attract the opposite permanent dipole in a neighbouring molecule.
- 39Van der waals' forcesForces arise due to movement of electrons (uneven distribution.) This causes an instantaneous dipole (temporarily.) This temporary dipole induces a dipole in neighbouring molecule. Dipoles attract one another (weak VDW's)
- 40Increasing van der Waals' forcesVDW's forces increase with an increase in the number of electrons. More electrons result in larger temporary and induced diploles, which results in a greater force of attraction between molecules. Therefore boiling point increases.
- 41Hydrogen bondingSpecial permanent dipole-dipole force between O-H or N-H bonds. The H△+ attracts the lone pair of electrons in the O△-/N△- in neighbouring molecule.
- 42Special properties of waterIce is less dense than water: the hydrogen bonds hold H2O molecules further apart in an open lattice.
H2O has a higher than expected boiling point: hydrogen bonds are the strongest intermolecular force therefore require more energy to break. - 43Simple molecular latticeE.g. H2 I2 H2O
Low melting/boiling points: weak VDW's forces require little energy to be broken. Don't conduct electricity: no free charged particles. - 44Giant covalent latticeE.g. Si, SiO2, diamond&graphite
High melting/boiling point: strong covalent bonds require lots of energy to break. Don't conduct electricity: no free moving charged particles - 45DiamondGiant covalent lattice. Doesn't conduct electricity: no free moving charged particles. Hard: strong covalent bonds throughout tetrahedral structure.
- 46GraphiteGiant covalent lattice with layers of carbon atoms. Conducts electricity: delocalised electrons between carbon layers. Soft: weak VDW's forces between the layers allowing them to slide.
- 47Ionic compoundsHigh melting/boiling point: strong electrostatic force of attraction between oppositely charged needs to be broken. Don't conduct in solid state: fixed position. Conduct when liquid/aqueous: ions free to move. Soluble in polar solvents, surround and break down lattice.
- 48Metal bondingThe strong electrostatic force of attraction between positive metal ions and delocalised electrons. High melting/boiling point: strong electrostatic force of attraction. Conduct electricity: delocalised electrons are free to move. Ductile: drawn out (wires.) Malleable: hammered into shape.
- 49ionic charge affecting melting point of a metalE.g. Na+ Mg2+ Al3+
As ionic charge increases the number of delocalised electrons increases. Therefore attraction increases between delocalised electrons and metal ions (stronger metallic bonding.)