Bonding

Beth Ritchie
Flashcards by Beth Ritchie, updated more than 1 year ago
Beth Ritchie
Created by Beth Ritchie over 7 years ago
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Chemistry (Bonding) Flashcards on Bonding, created by Beth Ritchie on 12/03/2013.

Resource summary

Question Answer
Define covalent bonding The sharing of pairs of electrons, usually between non-metal atoms, to form molecules or giant structures
What holds covalently bonded atoms together? The electrostatic attraction between the positive nuclei and the negative electron pairs shared between those nuclei
Define ionic bonding The net electrostatic attractions between oppositely charged ions in a 3D lattice, which usually occurs between metal and non-metal atoms
How are ions formed? By atoms losing or gaining electrons. More electronegative atoms gain electrons from less electronegative atoms
How are ions arranged? In a giant lattice structure, with cations and anions arranged alternatively
How stron is the lattice? Very strong due to strong electrostatic attractions
What is the melting point of ionic compounds, and how does it's structure explain this? Ionic compounds have very high melting points, as the strong electrostatic forces need to be broken
What is the conductivity of ionic compounds, and how does it's structure explain this? In solid form, ionic compounds cannot conduct as charged ions cannot move. However, when molten or in solution, ionic compounds can conduct
What is the bonding in metals, and how to they remain bonded together? Metallic - each atom is detached from it's outer electrons, forming metal cations and a sea of delocalised electrons between which there is an electrostatic attraction
How does the metallic bonding model explain the conductivity of metal? The delocalised electrons can carry charge when the metal is in solid or liquid state
How does conductivity change from Na to Mg to Al? Because Na has 1 delocalised electron, Mg has 2 and Al has 3, they are more conductive respectively as there are more delocalised electrons to carry charge
How does the metallic bonding model explain the mallebility of metal? Because layers of cations can slide over eachother without breaking the bonds as the delocalised electrons keep them bonded
What is the melting point trend down metal groups? It decreases, as there is a larger atomic radius and therefore a weaker electrostatic attraction
What is the melting point trend across metal periods? Increase, due to an increased number of delocalised electrons and an increased charge, so stronger electrostatic attraction to hold the atom together
What acronym explains the 3-D shapes of molecules? VSEPR - Valance Shell Electron Pair Repulsion
What does the acronym mean? Electron pairs repel eachother and get as far apart as possible to minimise repulsions
What happens to a molecules shape if only bond pairs are present? The shape will be totally symetrical
When two atoms are bonded to a central atom with no lone pairs, what is it's shape and bond angle? Linear, 180 degrees
When three atoms are bonded to a central atom with no lone pairs, what is it's shape and bond angle? Trigonal planar (meaning it is on one plane), 120 degrees
When four atoms are bonded to a central atom with no lone pairs, what is it's shape and bond angle? Tetrahedral, 109.5 degrees
When five atoms are bonded to a central atom with no lone pairs, what is it's shape and bond angle? Trigonal bipyramid, 90 degrees and 120 degrees
When six atoms are bonded to a central atom with no lone pairs, what is it's shape and bond angle? Octahedral, 90 degrees
Where are lone pairs relative to bond pairs? Closer to the nucleus due to electrostatic attraction
What happens to 'normal' (symmetrical) angles when lone pairs are present? Reduced by about 2.5 degrees per lone pair present
When three atoms are bonded to a central atom with a lone pair, what is it's shape and bond angle? Trigonal pyramid, 107 degrees (109.5-2.5)
When two atoms are bonded to a central atom with two lone pairs (eg. Water), what is it's shape and bond angle? V-shape, 104.5 (109.5 - 5)
What IMF's are between ionic compounds? None
What IMF's are between metallic? None
What IMF's between giant covalent? None
What IMF's are between molecular covalent? Van der Waals (for all), dipole dipole (for polar molecules) and hydrogen bonds (for H-F, H-N or H-O)
What is the melting point of ionic compounds and why? Very high, because strong electrostatic attractions must be overcome
What is the melting point of metallic? Very high (except Hg) and lots of energy is needed to overcome strong electrostatic attractions between cations and delocalised electrons
What is the melting point of giant covalent? Very high, as they need lots of energy to break strong covalent bonds
What is the melting point of molecular covalent? Low, as generally very little energy is needed to overcome weak IMF's but melting point varies on type of IMF and molecular size
What is the conductivity of ionic? None, unless molten or in solution
What is the conductivity of metallic? Very high, because delocalised electrons move
What is the conductivity of giant covalent? Insulators, as there are no charged particles present, except for graphite which has delocalised electrons
What is the conductivity of molecular covalent? Insulators - no charged particles present
What bonds are present in diamond? 4 strong covalent bonds ber carbon atom
What shape is diamond? Tetrahedral
What is diamond's bond angle? 109.5 degrees
What are 3 properties of diamond? High melting point, hard and non-conducting
What type of structure is diamond? Giant covalent
What type of structure is graphite? Giant covalent
What kind of bonds are in graphite? 3 strong covalent bonds per carbon atom, leading to 1 delocalised electron per carbon atom
What is the shape of graphite? Trigonal planar, with planes of carbon atoms in hexagons
What is the bond angle in graphite? 120 degrees
What are 3 properties of graphite? High melting point, soft due to sliding layers and conductive due to delocalised electrons
What is the structure of NaCl? Giant ionic
What is the shape of NaCl? Cubic
What is the coordination of NaCl? 6:6
What are 3 properties of NaCl? High melting point, non conducting when solid, but conducts when molten or in solution
What is the trend in first ionisation energies across period 3? General increase as nuclear charge increases, but decreases between Mg-Al as outer electron is in more distant and shielded 3p orbital, and decrease P-S due to e- pair causing repulsions
What is the trend in melting points across period 3? Increases Na-Al as metallic bonds with more delocalised electrons, Si is higher due to strong covalent bonds, then P-Ar lower due to VW forces
What is the trend in boiling points across period three? Increases Na to Al, as delocalised electrons increases, decreases Al-Si because vaporisation occurs when enough covalent bonds are broken to create Si2 and Si3 molecules, then VW forces
What is the trends in conductivities across period three? Increase due to metals with more delocalised electrons, Si is a semi conductor, others are non-conducting
What are the trends in atomic radii across period three? Decrease, as greater nuclear charge and same atomic radius and shielding
What are the trends in first ionisation energies down group two? Decrease as electrons are more distant and more shielded
What are the trends in atomic radii down group two? Increase as energy levels are added
What are the trends in electronegativities down group two? Decrease as bond electron is more distant and more shielded from nucleus
What are the trends in melting points down group two? Decreasae as metallic bonding is weaker because radius and mass of 2+ ions increase, reducing strength of electrostatic attraction
What are the trends in electronegativities across period three? Increase due to increasing nuclear charge
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