Electrons, Bonding And Structure

Question 1

Spin pairing

Answer 1

2 electrons in orbital ‘spin’ in opposite directions

Question 2

Electron configuration

Answer 2

Number of electrons an atom/ion has and their arrangement

Question 3

Exception: Chromium/copper, electrons spread out

Answer 3

• subshells v close in energy
• reduces repulsion
• extra stability from half/full 3d subshell

Question 4

Ionic bonding

Answer 4

Strong electrostatic attraction holds oppositely charged ions together. Ions formed by transfer of electrons

Question 5

Ionic structure

Answer 5

• giant ionic lattice
• packed alternately in regular lattice
• same basic unit repeated (giant)
• each ion elect.attr. in all directions to oppositely charged ions
• cube shaped NaCl

Question 6

Ionic behaviour

Answer 6

• conducts electricty when molten/dissolved- ions free to move and carry charge, not fixed position by strong ionic bonds
• high mpt- lots of energy needed to overcome strong electrostatic forces
• soluble in water- polar water molecules attract charged ions, pulling them away from the lattice

Question 7

Electronegativity

Answer 7

• Atom’s ability to attract bonding electrons in a covalent bond.
• Increases across period & up group (F).
• Measured on Pauling scale

Question 8

Dipole

Answer 8

Difference in charge between 2 atoms because of shift in electron density in covalent bond

Question 9

Polarising covalent bonds

Answer 9

• bonding electrons pulled towards more EN atom
• bond is polar (slightly neg/pos ends)
• difference in EN causes permanent dipole

Question 10

Polar bond

Answer 10

• difference in electronegativities between atoms in a molecule
• one end slightly pos, other slightly neg (as electrons attracted to more EN atom)

Question 11

Non polar bond

Answer 11

• Atoms have equal/similar electronegativities

- incl C-H bonds

Question 12

Polar molecule

Answer 12

Depends on arrangement of polar bonds
Draw and label molecule first

• polar bonds asymmetrical
• dipoles don’t cancel out
• charge arranged unevenly across whole molecule
• overall dipole (polar)

Question 13

Non polar molecule

Answer 13

• polar bonds arranged symmetrically
• dipoles cancel out
• no overall dipole (non polar)

Question 14

Ionic or covalent?

Answer 14

V few compounds are completely ionic/covalent

EN difference=0 (diatomic) means purely covalent
Greater EN difference= more ionic in character

Covalent HCl gas dissolves into ionic HCl acid soln

Question 15

Intermolecular forces

Answer 15

Forces between molecules
Much weaker than covalent/ionic/metallic bonds
3 types

Question 16

Induced dipole-dipole (London/dispersion)

Answer 16

Between non-polar molecules (eg noble gases/halogens)
- Random movement of e (in charge clouds)
- uneven distribution of e
- instantaneous temp dipole in 1 molecule
- induces dipole in neighbouring molecule (to which it then attracts)
Increase/stronger as number electrons increases
Constantly being created/destroyed (constantly moving)

Question 17

Permanent dipole-dipole

Answer 17

Polar molecules
Delta charges cause weak electrostat. forces between molecules
In addition to induced d-d

Question 18

Hydrogen bonding

Answer 18

V polar molecules: H-F, H-O, H-N
Electron deficient H atom in one molecule attracts lone pair on e on a very EN atom (N, O or F) in neighbouring molecule

Show: delta charges, lone pairs, shape & H-bond

Question 19

Orbital

Answer 19

Bit of space around the nucleus that an electron moves in. Orbitals in same subshell have same energy
S orbitals=spherical
P orbitals=dumbbell shaped, r angles to each other