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Flashcards in 2 - Bonding And Structure Deck (35)
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1

Giant covalent bonds?

Giant regular lattice
Sharing of electrons
Always solid at room temperature
Hard
Insoluble

2

Graphite?

Arranged in layers
each atom is bonded to 3 other atoms
Conductive

3

Small covalent molecules?

Low melting and boiling points because of weak intermolecular forces which break down easily.
Non conductive
Strong bonds between atoms, weak bonds between molecules
low melting and boiling points
Insulators

4

Metallic bonding?

Malleable because they're in layers
Sea of delocalised electrons, free to move throughout.
sharing of many detatched electrons between positive ions.
This gives them structure and explains why many metals have high boiling points

5

Define metallic bonding?

Is the force of attraction, between valence electrons and metal atoms

6

Ionic bonding?

Between a metal and a non metal.
Between atoms which give or receive electrons.
DON'T conduct when solid
Soluble
High melting and boiling points

7

Structure of ionic bonding?

Lattice structure
Regular ion arrangement, results in crystals being produced.
Electrostatic forces of attraction between ions, means a lot of energy is required to separate negative and positive ions.

8

Proving existence of ions?

The migration of coloured ions during the electrolysis of copper (11) and chromate (v1) solution.

Potassium manganate and the DC current

9

Electron repulsion theory?

Greatest forces of repulsion:
Lone pair lone pair
lone pair bonded pair
Bonded pair bonded pair

10

Lone pairs?

Repel as much as possible.
Take off 2.5 degrees for every lone pair
Affect the bond angle.

11

Shapes of molecules?

Depends on the number of pairs of electrons in the outer shell.
All shapes depends on the number of pairs!

12

Linear?

2 pairs
180 degree bond anlge

13

Trigonal planar?

3 pairs
120 degrees

14

Tetrahedral?

4 pairs
104.5, 107, 109.5 degrees depending on lone pairs

15

Trigonal bipyramid?

5 pairs
90, 120, 180 degrees

16

Octahedral?

6 pairs
90, 180 degrees

17

What are the most electronegative elements?

N,O,F
nitrogen, oxygen, flourine

18

Define electronegativity?

Is the tendancy to attract the shared pair of electrons

19

Dative bonds?

Are formed when an ion attaches to the lone pair of an atom

20

Non polar molecules, eg O2?

Oxygen have the same electronegativity, therefore the electrons are equally shared between the atoms

21

Polar molecules eg, H2O?

Oxygen has a higher electronegativity than hydrogen, so the electrons will spend more time closer to the oxygen atom. This results in a partial negative charge around the oxygen atom.

22

What did Pauling do?

Assigned every element its electronegativity.

23

London Forces?

Occur between all molecules.
Fleeting repulsions and attraction between nuclei of the atoms and the electron cloud.
Temporary displacement cause temporary dipoles.
Neighbouring molecules are induced with temporary dipoles (opposite charge)

24

Dipole, dipole?

Attractive forces between the positive end of 1 polar molecule and the negative end of another.
Occurs between 2 polar substances
Creates a semi charge, or dipole in molecule
effected by: electronegativity of atoms and number of electronegative atoms

25

Hydrogen bonding?

Occurs between molecules where hydrogen is bonded to N,O,F
There must be a lone pair of electrons
Always a bond angle of 180.

26

Polarity?

If the shape is symmetrical and the electrons are the same, it's non polar!

27

Solubiltiy?

Like dissolves like,,,
Polar dissolves polar
Non polar dissolves non polar

28

Why do polar solvents dissolve in polar substances?

because the partial charges in the polar solvent can hold onto the partial charges in the polar solute and dissolve.

29

Non polar and polar?

Won't dissolve with eachother because the molecules would rather remain, and use their partial charges to stick together with hydrogen bonds than with the non polar molecules.

30

Bond length and strength?

x ray diffraction allows chemists to look at structures. Microwave spectroscopy can give us info on bond angles.