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70 Cards in this Set
- Front
- Back
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What is the trend of electronegativity down a group?
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Decreases
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Why does electronegativity decrease down a group?
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The size of the atom increases down a group meaning the bonding pair of electrons gets further away from the nucleus of the atom.
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What is electronegativity?
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A measure of the attraction of an atom in a molecule to the electron pair in the covalent bond of which it is a part.
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What is the trend of electronegativity across a period?
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Increases
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Why does electronegativity increase across a period?
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Nuclear charge increases across the period but there is no significant change to the amount of shielding.
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What is 'first ionisation energy'?
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The energy required to remove one electron from each atom in one mole of gaseous atoms under standard conditions.
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What is the trend of first ionisation energy down a group?
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Decreases
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Why does first ionisation energy decrease down a group?
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The size of the atom increases meaning that the valence electron is further from the nucleus and therefore less strongly attracted by the nucleus.
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What is the general trend of first ionisation energy across a period?
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Increases
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Why does first ionisation energy generally increase across a period?
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Protons are added to the nucleus but shielding has minimal change meaning that the force from the nucleus is stronger across a period.
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What is the trend of atomic radius down a group?
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Increases
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Why does atomic radius increase down a group?
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Atoms have more shells as you go down a group
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What is the trend of atomic radius across a period?
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Decreases
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Why does atomic radius decrease across a period?
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Nuclear charge increases across a period but shielding has no significant increase. Outer electrons are pulled in more strongly.
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What is the pattern of ionic radii of positive ions, relative to their atomic radii?
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The ionic radii of positive ions are smaller than their atomic radii.
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Why are the ionic radii of positive ions smaller than their atomic radii?
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For some ions, a shell of electrons has been lost (1 electron in the outer shell). Also, there is the same nuclear charge but there is more electron-electron repulsion in the atom than the ion because there are more electrons, thus making the electron cloud larger in the atom.
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What is the pattern of ionic radii of negative ions, relative to their atomic radii?
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The ionic radii of negative ions are larger than their atomic radii.
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Why are the ionic radii of negative ions larger than their atomic radii?
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The ion has more electrons but the same nuclear charge meaning that there is greater repulsion between electrons. Electron cloud expands as a result.
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What is the general trend of ionic radius for positive ions across a period?
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Decreases as the charge on the ion increases
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What is the general trend of ionic radius for negative ions across a period?
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Increases as charge on the ion increases
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Why is the ionic radius of Mg2+ smaller than that of Na+ even though they have the same electronic configuration?
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Mg2+ has one more proton in the nucleus meaning despite the equal electron-electron repulsion, there is a higher nuclear charge in Mg2+. This means that the electrons are oulled in more strongly resulting in a smaller ionic radius.
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What is the trend of melting point down group 1?
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Decreases
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What is the trend of melting point down group 7?
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Increases
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Why does melting point decrease down group 1?
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All elements in group 1 have metallic bonding. As you go down the group, the ion gets larger meaning that the nucleus is further from the delocalised electrons and the attraction is weaker. Less energy is therefore required to break apart the lattice.
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Why does melting point inrease down group 7?
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As the relative molecular mass of the halogens increases, the Van der Waal's between molecules become stronger meaning that it takes more energy to separate the molecules.
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What is the trend of melting point across period 3?
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It varies due to the different types of bonding in the elements.
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What is the trend of melting point from Na to Mg to Al?
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Increases
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Why is there a large increase of melting point from Al to Si?
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Silicon has a giant covalent structure.
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What is the bonding in Na, Mg and Al?
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Metallic
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After Si, what happens to the trend of melting points?
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There is a sharp decrease from Si to P as the bonding changes to covalent molecular. The melting point of P is much lower because only weak Van der Waal's forces must be broken.
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Why is the melting point of S higher than P?
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Sulphur forms S8 and P only forms P4 meaning that sulphur has a higher relative molecular mass. More energy is required to break the VDW's in S8 than in P4.
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What is the trend of melting point from S to Ar?
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Decreases
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Why does melting point decrease from S to Ar?
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The relative mass of the molecule (atom for argon) decreases meaning the amount of VDW's forces decreases.
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How well do the group 1 elements react?
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They are very reactive and react more vigorously as you go down the group because the ionisation energy decreases.
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What is the equation for the general reaction between a group 1 element and oxygen?
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4M + O2 → 2M2O
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What is the general equation for the reaction between a group 1 element and water?
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2M + H2O → 2MOH + H2
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How do the group 1 elements (alkali metals) react with oxygen and water?
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They react vigorously with oxygen and rapidly with water. In water, an alkaline solution is formed.
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What is the trend in reactivity of the group 7 elements?
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Decreases down the group
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How does potassium chloride (KCl) react with Cl2, Br2 and I2?
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There is no reaction.
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How does potassium bromide (KBr) react with Cl2, Br2 and I2?
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It forms an orange solution with Cl2 and there is no reaction with Br2 and I2.
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How does potassium iodide (KI) react with Cl2, Br2 and I2?
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It forms a dark red/brown solution with Cl2 and Br2 but there is no reaction with I2.
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What is meant by 'displacement reactions of halogens'?
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Reactions between a solution of a halogen and a solution containing halide ions.
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Why aren't scandium and zinc considered to be transition elements/metals?
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Scandium has no d electrons and zinc has a full d subshell. Neither form coloured compounds.
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What are the characteristic properties of transition metals?
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- All are typical metals (high MP and densities)
- Exhibit more than one oxidation number in compounds/complexes - Form complex ions - Usually form coloured compounds/complexes - With their compounds/complexes, they can act as catalysts in many reactions |
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What type of ion do transition elements form?
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Positive
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What is the oxidation number that is common to all transition metals?
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+2
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Do transition metals exhibit just one oxidation number?
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No, they have variable oxidation numbers.
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Which transition elements can have oxidation number of +3 as well as +2?
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Fe and Cr
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Which transition element can have oxidation number +4 as well as +2?
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Mn
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Which transition element can have oxidation number +6 as well as +2?
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Cr
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Which transition element can have oxidation number +7 as well as +2?
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Mn
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What do complex ions consist of?
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A central transition metal ion surrounded by ligands
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What is a ligand?
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Negative ions or neutral molecules that use lone pairs of electrons to bond to a transition metal ion to form a complex ion. Dative covalent bonds are formed between the ligand and the transition metal ion.
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In terms of acids and bases, what is a ligand?
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A Lewis base
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Give 3 neutral ligands.
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H2O, NH3 and CO
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Give 3 '1-' ligands.
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Cl-, CN- and Br-
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What is the usual shape of a six coordinate complex?
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Octahedral
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What are the possible shapes of four coordinate complexes?
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Tetrahedral or square planar
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Why do transition metal form coloured compounds?
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They have partially filled d subshells which split into two of different energy levels. Electrons can absorb certain frequencies of light and move between the two levels making them appear coloured.
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Which transition metal is used as a catalyst in the Haber process?
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Iron
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Which transition metal complex is used as a catalyst in the Contact process?
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Vanadium (V) oxide
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Which transition metal complex is used as a catalyst in the decomposition of hydrogen peroxide?
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Manganese (IV) oxide
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Why are catalysts important in the Contact and Haber processes?
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They increase the rate of reaction and mean that the reaction can be run at a lower temperature, saving fuel whilst still improving yield. This is more cost effective overall.
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What colour is chromate (VI), [CrO4]2-?
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Yellow
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What colour is dichromate (VI), [Cr2O7]2-?
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Orange
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What is the oxidation state of manganese?
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+7
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What colour is the manganate (VII) ion?
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Dark purple
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What is the most stable oxidation state of copper?
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+2
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What colour is the [Cu(H2O)6]2+ ion in aqueous solution?
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Pale blue
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What colour are the majority of copper(I) compounds and what is the exception?
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White/colourless because they have a full 3d subshell. However, copper (I) oxide, Cu2O is red.
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