atomic structure

Question 1

scientists interested in atomic structure?

Answer 1

Heisenberg, Pauli, Schrodinger, Bohr, De Broglie, Einstein, Planck

Question 2

Democritus

Answer 2

dividing any piece of matter to smaller parts until indivisible and named it “atom”

Question 3

Aristotle

Answer 3

all matter whatever its nature -is composed of four components ( fire-air - dust -water)

Question 4

what concept did Aristotle reject?

Answer 4

Aristotle rejected the concept of atom

Question 5

why was Aristotle the reason chemistry science didn’t develop for more than thousand years?

Answer 5

because the scientists were busy trying to change cheap metals into precious ones

Question 6

Boyle

Answer 6

gave the first definition of element

Question 7

whats the definition of element?

Answer 7

Element:
its a pure simple substance that can’t be changed into simpler forms

Question 8

what idea did Boyle reject?

Answer 8

Boyle rejected Aristotle’s idea

Question 9

scientist that said that the substances consists of very small particles called “atom”

Answer 9

Dalton

Question 10

Dalton said that every element consists of?

Answer 10

very small dense atoms (solid) particle which can’t be divided

Question 11

what did Dalton say about atom masses?

Answer 11

masses of atoms of the same element are similar but differ from one element to another

Question 12

what did Dalton say about the compounds?

Answer 12

the compounds are formed by the combination of atoms of different elements in simple numerical ratio

Question 13

Thomson

Answer 13

gases don’t conduct electricity under normal conditions of pressure and temperature

Question 14

under what conditions do gases conduct electricity?

Answer 14

in a discharge tube with high potential difference and very low pressure

Question 15

cathode rays

Answer 15

are streams of invisible rays emitted from the cathode of a discharge tube in which the pressure of the gas is very low and the potential difference between the two electrodes is about 1000 volts

Question 16

what are those rays composed of?

Answer 16

composed of minute particles named “electrons”

Question 17

what is the charge of the cathode rays?

Answer 17

the cathode rays are negatively charged

Question 18

what direction do the cathode rays move?

Answer 18

in straight lines except if there is electric or magnetic fields

Question 19

cathode rays don’t change by?

Answer 19

by changing either cathode material or type of the gas

Question 20

other properties of cathode rays:

Answer 20

they’re invisible
have thermal effect

Question 21

The Postulate of Thomson’s model

Answer 21

the atom is a solid sphere positively charged in which a number of negatively charged electrons embedded to make the atom electrically neutral

Question 22

Rutherford’s students

Answer 22

Geiger and Marsden

Question 23

what tools did Geiger and Marsden use to experiment Rutherford’s theory?

Answer 23

a metal sheet lined with a layer of zinc sulphide

gold foil

Question 24

why did Geiger and Marsden use a metal sheet lined with a layer of ZnS?

Answer 24

because it glows when alpha rays collide with ZnS

Question 25

why did Geiger and Marsden use gold foil?

Answer 25

because it doesn’t react with alpha particles

Question 26

why does the ray pass in straight lines without breaking?

Answer 26

this means that the ray passes in an empty space.most of the atomic volume is an empty space not a solid ball as proposed by Dalton and Thomson

Question 27

why does the ray deviate?

Answer 27

the dense part of the atom (the nucleus) has a positive charge similar to that of alpha-particles

Question 28

why does the ray deflect?

Answer 28

the atom contains a tiny part of very high density, atomic mass concentrated in the nucleus

Question 29

the postulates of Rutherford’s atomic theory: ( atom )

Answer 29

the atom resembles the solar system in which electrons revolve around the central nucleus in orbits as planets revolve around the sun

Question 30

the postulates of Rutherford’s atomic theory: ( nucleus )

Answer 30

.the nucleus is smaller than the atom
.atomic mass is concentrated in the nucleus
.it is positively charged
.it has a vast space between the nucleus and the orbits of electrons

Question 31

the postulates of Rutherford’s atomic theory:
what is the electron’s mass compared to the nucleus

Answer 31

.the electron has a negligible mass compared to that of the nucleus
.

Question 32

drawback of Rutherford’s atomic model:

Answer 32

because it didn’t explain the system in which electrons revolve around the nucleus

Question 33

the postulates of Rutherfords atomic theory:
what is the electrons charge

Answer 33

charge is negative and equals the nuclear positive charge ( the atom is electrically neutral )

Question 34

the postulates of Rutherfords atomic theory:
what is the movement of electrons

Answer 34

electrons revolve around the nucleus in a fixed orbit

Question 35

the postulates of Rutherfords atomic theory:
what is the electrons affected by

Answer 35

affected by two forces equal in strength but in opposite direction
*force of attraction of the nucleus to electrons
*centrifugal force due to velocity of electron around the nucleus