C1.2 Atomic structure

Question 1

What is a molecule?

Answer 1

Two or more atoms joined by attractive forces called CHEMICAL BONDS

Question 2

Size of an atom:

Answer 2

given by atomic radius

Typically around 10^-10

Question 3

Size of bond length:

Answer 3

Distance between the centres of two joined atoms

Typically 10^-10

Question 4

What 3 subatomic particles are inside of an atom?

Answer 4

Proton
Neutron
Electron

Question 5

What is the radius of a nucleus?

Answer 5

Approx 100,000x less than radius of an atom

Question 6

Mass and charges of the subatomic particles:

Answer 6

Proton: 1 , +1
Neutron: 1 , 0
Electron: 0.0005 , -1

Question 7

What does the chemical symbol show?

Answer 7

atomic Number - amount of protons in the nucleus

Atomic Mass - Total number of protons and neutrons

Question 8

What is an isotope?

Answer 8

Same element with different number of neutrons

Same atomic number but different atomic mass

Question 9

What is an ion?

Answer 9

Charge particles formed when atoms lose or gain electrons.

Question 10

What is Daltons Model - The Billiard Ball?

Answer 10

Atoms are solid spheres
Atoms of a given element are the same
Atoms of different elements are different to each other

Question 11

What research did Dalton do?

Answer 11

No experiments to investigate atoms

Therefore he had no evidence to support his ideas

Question 12

What is Thompsons Model - The Plumb Pudding?

Answer 12

An atom is a solid sphere of positive charge

Electrons are tiny, neg charged particles embedded in the atom

Atoms have no net charge because total positive charges in the atom cancel out the total neg charges

Question 13

What did Thompson do?

Answer 13

Placed electrodes in glass tubes
Applied a high voltage across the electrodes
Produced cathode rays

Question 14

Problem with Thompsons Model

Answer 14

Geiger & Marsden’s gold foil experiment obtained results that Thompson’s model could not explain
As a result the atomic model had to be revised

Question 15

What did Rutherford do?

Answer 15

His pupils Geiger and Marsden fired pos-charged Alpha particles at gold foil
A Zinc Sulfide screen was placed around the foil to detect where the particles would end up

Question 16

Results of Rutherford’s experiment

Answer 16

Most alpha particles went straight through

Rest of alpha particles either went through the foil and deflected at large angles or bounced off the foil

Question 17

What was Rutherford’s Model of the atom? - the planetary/nuclear model

Answer 17

The atom is mostly empty space
Containing a concentration of mass in the centre
the centre must be pos charged
With electrons randomly orbiting the nucleus like planets around a sun

Question 18

Problems with Rutherford’s model

Answer 18

Bohr went over his data and did calculations:
If Rutherford’s was true, the electrons should eventually crash into the nucleus because the pos charge of the nucleus would attract the neg charged electrons

Question 19

What was Bohr’s Model? - The orbital model

Answer 19

The atom is mostly empty space
Containing a concentration of mass in the centre
the centre must be pos charged
With electrons orbiting the nucleus on fixed electron shells
To be on a certain shell, an electron had to have a certain amount of energy

Question 20

DaTe RnBo

Answer 20

Dalton, atom
Thompson, electron
Rutherford, nucleus
Bohr, orbitals