Atomic Structure

Question 1

Atom

Answer 1

is the smallest unit of matter that retains all of the chemical properties of an element

Question 2

Law of conservation of mass

Answer 2

states that matter cannot be created or destroyed in a chemical reaction.

Question 3

Atomic number (Z)

Answer 3

the number of protons in the nucleus of an atom of that element. It also corresponds to the number of electrons in the neutral atom.

Question 4

Mass number (A)

Answer 4

the number of protons and neutrons in an atom of the element.

Question 5

Relative Atomic Mass (Ar)

Answer 5

The mass of an atom of that element compared with one twelfth of the mass of the carbon-12 isotope.

Question 6

Relative Molecular Mass

Answer 6

The mass of a molecule of that substance compared with one twelfth of the mass of the carbon-12 isotope

Question 7

Isotope

Answer 7

Atoms of the same element but which differ in the numbers of neutrons in their nuclei (or, have different mass numbers)

Question 8

All matter is made of small particles

These particles can be…

Answer 8

Atoms
Ions (charged atoms)
Molecules (groups of atoms)

Question 9

Outline the contribution of the following to atomic theory and atomic structure: Greeks

Answer 9

All matter is made of minute particles

Greek word for invisible is ‘atomos’

Question 10

Outline the contribution of the following to atomic theory and atomic structure: Dalton

Answer 10

Developed atomic theory

• All matter is made of very small particles called atoms
• Atoms are indivisible, they cannot be broken down
• Atoms cannot be created or destroyed

Question 11

Outline the contribution of the following to atomic theory and atomic structure: Crookes

Answer 11

• Developed cathode rays using a vacuum tube
• Passed an electric current through a vacuum tube
• Noticed that radiation was coming from the negative electrode (cathode)
• Called these rays cathode rays

Question 12

Cathode rays are…

Answer 12

• Streams of negatively charged particles called electrons
• Travel in straight lines from the cathode to the anode
• Are deflected by electric and magnetic fields
• Have enough energy to move a small object such as a paddle or a wheel

Question 13

Outline the contribution of the following to atomic theory and atomic structure: JJ Thompson

Answer 13

Discovered the electron.
He found that cathode rays are attracted to positive plate and so must be made of negatively charged particles = electrons
2. He calculated the charge to mass ratio (e/m) for the electron
3. He proposed the plum pudding model of atomic structure. An atom is a positive sphere with negative particles stuck in it.

Question 14

who named the electron

Answer 14

This name was first proposed by an Irishman named George Stoney

Question 15

what is the ratio of the charge of the electron (how negative it is) to the mass of the electron

Answer 15

e/m of the electron

Question 16

Outline the contribution of the following to atomic theory and atomic structure :Rutherford

Answer 16

• Discovered the nucleus
  Shot alpha particles at a sheet of gold foil
  Expected alpha particles to pass straight through atoms with slight deflections
  Most of the alpha particles did pass through 🡪 most of the atom must be made of empty space
  some alpha particles were reflected at large angles and some were reflected back along their own path!
  Concluded that there must be a dense core of positive charge within the atom
  This small dense core was called the nucleus of the atom

Also discovered protons!
Bombarded many elements with alpha particles
Positive charges were emitted from the nuclei of lighter elements
Alpha particles were breaking up the nuclei of the lighter elements ad releasing the positive charges
These positive charges were called protons