History of the atom.2

Question 1

What is a atom

Answer 1

The smallest part of an element which still has the properties of that element

Question 2

What is an Element

Answer 2

substance that cannot be broken down into anything simpler by chemical means

Question 3

Matter

Answer 3

Anything which takes up space and has mass

Question 4

What did the Greek philosophers propose

Answer 4

Matter was composed of small particles, these particles were so small they couldn’t be broken down into smaller particles (indivisible)

Question 5

What did John Dalton develop

Answer 5

John Dalton developed the atomic theory

Question 6

What is the atomic theory

Answer 6

All matter is made up of tiny indivisible particles called atoms that can be neither created nor destroyed. Atoms of the same element have identical atomic number

Question 7

Who conducted the first experiments on cathode rays

Answer 7

William crookes

Question 8

What is william crookes contributation?

Answer 8

Descovered cathode rays
descovered cathode rays musts consist of very small particles

Question 9

describe the expeirment by crookes that discovered cathode rays and the obervations that occoured

Answer 9

passed electric current through a vacuume tube
(one with the maltease cross)
Observations: florsence in glass tube opposite to cathode
shadow coming from cross

Question 10

what did crookes conclude when he conducted the expeirment on discovering cathode rays

Answer 10

radiation coming from the cathode

Question 11

describe his second/ futher expeirment on cathose rays and describe his obervations

Answer 11

placed electric current through pressure vacum tube with light paddle wheel in center.
Observations: paddle wheel moves away from cathode.
cathode rays consist of very small particles

Question 12

What did crookes conclude from his second expeirment on cathode rays

Answer 12

cathode rays consist of very small particles

Question 13

who was the irish scientist that proposed the name electron

Answer 13

stoney

Question 14

Who disovered the electron

Answer 14

JJ.thompson

Question 15

name jj thomson’s contrubutions

Answer 15

discovered the electron
decrovered that electrons were negativily charged,discovered the charge to mass ratio of an electrom

Question 16

Decribe JJ.thomsons expeirment on cathode rays and his obervations

Answer 16

passed cathode rays through tube in anode and low pressure vaccum tube.
placed two charged plated on either side (electric field).
when the plated where charged, the fluorsence caused by the glass being stuck appeared closer to the postive plate

Question 17

Name the model of the atom that Thompson proposed

Answer 17

Plum pudding model

Question 18

describe the model

Answer 18

a overall postive charge with electrons randomly embedded throughout . the atoms balances netural.

Question 19

what are cathode rays

Answer 19

beams of negatively charged electrons

Question 20

name properties of cathode rays

Answer 20

consists of negatice electrons
cause glass to floursence when struck
have enough energy to move a paddle wheel
are attracted to postive electric forces

Question 21

name contrubutions did robert milikan

Answer 21

calculated an electron’s charge , exact charge to mass (oil drop expeirment)

Question 22

who disovered the nucleus

Answer 22

ernest rutherford

Question 23

name ernest rutherfords contributions

Answer 23

descovered the nucleus ( disproved plum pudding midel)
discovered postive protons in nucleus

Question 24

what are alpha particles

Answer 24

consist of 2 protons and 2 neturnal emitted by radioactive isotopes trying to become stable
identical to helum nucleus
+2 charge

Question 25

desctibe the goil foil expeirment

Answer 25

Bombared a thin gold foil with alpha particles. alpha particles from a radioactibve souce with a lead box

Question 26

Describe the expected results of the goil foil expeirment

Answer 26

most of the alpha particles would go straight through undefelected or slight reflections

Question 27

Describe the actual results of the goil foil expiernent

Answer 27

some alpha particles were deflected at large angles
a tiny number of alpha perticles refelected completely back along its orginal path, this could not be explained using the plum pudding model

Question 28

what did rutherford, after his expeirment, conclude about the atom

Answer 28

-atoms were mostly empty space- most alpha particles passed through.
-the area in the center of an atom must be very small- postively charged and dense (some rebounded along its orginal paths)
-electrons must reside in an electron cloud surrounding the nucleus

Question 29

describe the atomic / nuclear model of the stom

Answer 29

electrons in an electron cloud- the nucleus is small, postive dense. the atom is mostly empty space

Question 30

what was james chadwick’s controbution

Answer 30

descovered the netron in the nucleus that has no charge. last subatomic partile to be discovered.