Atomic Structure

Question 1

What are isotopes?

Answer 1

Atoms of the same element with different numbers of neutrons and different masses.

Question 2

What does a time of flight mass spectrometer do?

Answer 2

Discovers mass and abundance of each isotope and element.

Question 3

What happens in the ionisation chamber of a mass spectrometer?

Answer 3

• A sample is injected through the sample inlet.
• atoms enter chamber where a beam of electrons gun.
  -entire chamber kept under vacuum so that the ions cannot collide with air molecules.
  -the electron gun knocks an electron out of each atoms outer shell so that ions with a single positive charge are formed.

Question 4

What happens in the acceleration area of a mass spectrometer?

Answer 4

Once in this area, the ions are accelerated by an electronegative field, so that they all have the same kinetic energy.

Question 5

What happens in the drift region of a mass spectrometer?

Answer 5

The atoms enter the drift region with the same KE. This means their speed will be indirectly proportional to their mass.
The heavier they are, the slower they will travel.

Question 6

What happens in the ion detector of a mass spectrometer?

Answer 6

When the ions hit the detector an electrical current is created.

Question 7

What is ionic bonding?

Answer 7

The strong electrostatic attraction between ions of opposite charge.

Question 8

Why do most ionic compounds have high boiling and melting points?

Answer 8

There are strong forces of attraction in the giant ionic lattice which means that large amounts of energy are required to overcome the strong electrostatic attraction between the ions.

Question 9

In the solid state ions are…

Answer 9

in a fixed position in the giant ionic lattice and there are no mobile charge carriers.

Question 10

When ions are liquid or dissolved in water…

Answer 10

the solid ionic lattice breaks down and ions are now free to move as mobile charge carriers.

Question 11

What is covalent bonding?

Answer 11

The strong electrostatic attraction between two nuclei and a shared pair of electrons between them.

Question 12

What is a dative covalent bond?

Answer 12

A covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only.

Question 13

What is average bond enthalpy?

Answer 13

Serves as a measurement of covalent bond strength.

Question 14

What is the electron-pair repulsion theory?

Answer 14

A model used to explain and predict the shapes of molecules and polyatomic ions.

Question 15

What bond angle does a linear molecule have?

Answer 15

180 degrees

Question 16

What bond angle does a v-shaped molecule have?

Answer 16

104.5 degrees

Question 17

What bond angle does a trigonal pyramidal molecule have?

Answer 17

107 degrees

Question 18

What bond angle does a tetrahedral molecule have?

Answer 18

109.5 degrees

Question 19

What bond angle does a trigonal planar molecule have?

Answer 19

120 degrees

Question 20

What bond angle does an octahedral molecule have?

Answer 20

90 degrees

Question 21

Give the principles of electron pair repulsion theory.

Answer 21

Electron pairs around the central atom repel each other as far apart as possible.
The greater the number of electron pairs, the smaller the bond angle.
Lone pairs of electrons repel more strongly than bonded pairs of electrons.

Question 22

How is electronegativity measured?

Answer 22

The Pauling scale.

Question 23

What is electronegativity?

Answer 23

The attraction of a bonded atom for the pair of electrons in a covalent bond.

Question 24

What happens to nuclear charge and atomic radius across the periodic table?

Answer 24

The nuclear charge increases
The atomic radius decreases

Question 25

When is a bond non-polar?

Answer 25

when the bonded atoms are the same or have the same or similar electronegativity.

Question 26

In a non-polar bond, the bonded electron pair is shared...

Answer 26

equally.

Question 27

When is a bond polar?

Answer 27

When the bonded atoms are different and have different electronegativity values.

Question 28

In a polar bond the bonded electron pair is shared...

Answer 28

unequally.

Question 29

What is a dipole?

Answer 29

The separation of opposite charges.

Question 30

What are intermolecular forces?

Answer 30

Weak interactions between dipoles of different molecules.

Question 31

What are the four types of intermolecular forces?

Answer 31

- London forces - Permanent dipole - induced dipole - (Permanent) dipole - (permanent) dipole - hydrogen bonds

Question 32

What is metallic bonding?

Answer 32

The strong electrostatic attraction between free-moving delocalised electrons.

Question 33

What are London forces?

Answer 33

Weak intermolecular forces that exist between ALL molecules whether polar or non-polar.

Question 34

Which is the strongest type of intermolecular force?

Answer 34

Hydrogen bonding

Question 35

What type of molecules is hydrogen bonding found in?

Answer 35

H-F H-O H-N

Question 36

What is the weakest type of intermolecular force?

Answer 36

Induced dipole-dipole force (London forces)

Question 37

What type of molecules is permanent dipole-dipole forces found in?

Answer 37

Polar molecules

Question 38

How will the strength of induced dipole-dipole forces increase with size?

Answer 38

Larger atoms and molecules have more electrons and a greater volume of electron density that can become polarised, creating stronger temporary dipoles.

Question 39

How will the strength of induced dipole-dipole forces increase with surface area?

Answer 39

Molecules with a larger surface area also have stronger induced dipole-dipole forces of the electron cloud is exposed for interactions.

Question 40

What are permanent dipole-dipole forces?

Answer 40

Electrostatic attractions between the partial positive end of one polar molecule and the partial negative end of another.