Atomic Structure

Question 1

State the History of the Atom - John Dalton (1766-1844)

Answer 1

• Elements are composed of indivisible particles called atoms
• Atoms of the same element are identical
• Atoms of one element are different to atoms of any other element.
• Atoms of different elements combine in simple whole number ratios to form compounds.
• In chemical reactions atoms are rearranged, separated or combined - NEVER changed.

Question 2

State the history of the Atom - Joseph Thompson (1856-1940)

Answer 2

• Atoms sometimes eject a far smaller negative particle which he called an electron.
• An atom is made up of electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electron’s charge.

Question 3

State the history of the Atom - Ernest Rutherford (1871-1937)

Answer 3

• Helium nuclei are fired at a piece of gold foil a few atoms thick
• Although most pass through about 1 in 10,000 were deflected
  straight back
• Proposed a model with a central nuclei of positive charge with orbiting electrons held in place by electrostatic charge

Question 4

State the history of the Atom - Niels Bohr (1885- 1962)

Answer 4

• Using quantum theory added that the electrons were present in orbits.
• Each orbit can only hold a set number of electrons.
• 2n2

Question 5

State the history of the atom - James Chadwick (1891-1974)

Answer 5

• A problem with mass

Question 6

What early ideas are still held as true?

Answer 6

• Element
  Single pure substance that cannot be split into another substance
• Compound
  Chemically combined elements
• An atom
  Smallest particle of an element
• A Molecule
  Smallest part of a compound

Question 7

State the Atomic Structure charge and mass

Answer 7

Proton = 1.602 x 10-19 charge & 1.6726 x 10-27kg
Neutron - no charge & 1.6749 x 10-27kg
Electron = -1.602 x 10 -19 charge & 0.00091 x 10-27kg

Proton +1 & mass number 1
Neutron no charge & mass number 1
Electron -1 & mass number nil

Question 8

Electron behaviour in subshells

Answer 8

• Electrons always try and obtain the lowest energy state.
• Shells generally fill from inner level outwards.
• Need to be aware of subshells

Question 9

What is band theory?

Answer 9

• Valence band is the highest range of electron energies in which electrons are normally present at 0oK.
• Conduction band is where the electrons can move freely between atoms.

Question 10

What is an ion?

Answer 10

• An ion is an atom that has lost or gained an electron.
• Therefore it has an overall charge
• If an electron is removed from an atom it has an overall positive charge
• It is said to have been ionised.

Question 11

Explain binding energy in relation to potential energy

Answer 11

As binding energy reduces down the subshells from n to k, the potential energy increases from k to n.

Question 12

What is the unit used for energy?

Answer 12

• The ability to do work
• Unit is the Joule
• eV = electron volt
• 1eV equals approximately 160 zeptojoules (10−21 Joules)

Question 13

What are the 2 types of energy?

Answer 13

Potential
- Energy by reason of its mass and position or state.

Kinetic
-Energy of a body by reason of its
mass and motion.

Question 14

What is meant by conservation of energy and mass?

Answer 14

• Energy cannot be lost.
• It can only be converted from one to another.
• Energy has mass equivalence.

Question 15

What unit is used for power?

Answer 15

• Power is the rate at which work is done
• Unit is the Watt (W)
• 1W = 1Joule per second

Question 16

State the 3 types of heat transfer

Answer 16

• Conduction - movement of heat within same medium through vibrations.
• Convection - movement of heat within different mediums.
• Radiation - energy can travel without a medium.

Question 17

What is the equation for heat transfer?

Answer 17

Q=kA ΔT/ Δx
- Q = rate of heat flow
- K = thermal conductivity
- A = cross sectional area
ΔT = temperature difference
——
Δx