chapter 4: atoms

Question 1

in 400 BC, Democritus suggested that…

Answer 1

the universe is made up of invisible units called atoms

Question 2

what does atomos mean

Answer 2

uncut/indivisible

Question 3

who thought there were 4 elements in a substance, what were they?

Answer 3

aristotle; fire, earth, water, air (hot, cold, dry, wet)

Question 4

dalton’s theory

Answer 4

billard ball model - atoms are composed of small spheres like billard balls, every element is made up of tiny, unique particles

Question 5

JJ Thomson’s experiment

Answer 5

Cathode ray experiment - beam bends towards the positively charged plate on the outside tube, there must be negatively charged particles in the beam of light

Question 6

What did JJ Thomson discover

Answer 6

electrons

Question 7

What is JJ Thomson’s most famous model

Answer 7

The plum pudding model - negative electrons are embedded in a positive atom

Question 8

rutherford’s experiment

Answer 8

gold foil experiment - discovered nucleus of an atom, most off mass found in an atom is in the nucleus. he shot alpha particles through a thin sheet of foil, they are deflected if the get close enough to the atom

Question 9

what are he 3 main subatomc particles?

Answer 9

protons (inside nucleus), electrons (outside nucleus), neutrons (inside nucleus)

Question 10

why are atoms neutral?

Answer 10

each positive charge is balanced by negative charge

Question 11

Henry moseley

Answer 11

concept of an atomic number

Question 12

mass number

Answer 12

number of protons and neutrons

Question 13

isotopes

Answer 13

have the same number of protons but a different number of neutrons

Question 14

how is mass of an atom expressed

Answer 14

amu