3.1 Atomic Theory

Question 1

Democritus

Answer 1

matter is made up of particles in 460 BCE, based on reason not empirical evidence

Question 2

Lavoiser

Answer 2

used experimentst to get quantitave measurements of chemical reactions (Law of Conservation of MAss)

Question 3

Dalton

Answer 3

BILLIARD BALL MODEL - elements consist of atoms that cannot be created or destroyed or divided, and atoms of the same element have identical size, mass and other properties

Question 4

Thomson

Answer 4

PLUM PUDDING MODEL -In the 19th century applied high voltage to a cathode gas tube with a metal electrode at each end. observed a visible ray deflected away from the negative pole in an applied electric field. provided existence of the electron, theorized that atoms consist of cloud of positive charge with negatively charge electrons embedded randomly in it.

Question 5

Millikan

Answer 5

mass of an electron (9.11 x 10^-31 kg)

Question 6

radioactivity

Answer 6

Rutherford- theory of radioactivity/the disintegration of atoms/spotanous decay of nuclues

Question 7

Chadwick

Answer 7

discovered the existence of neutrons (uncharged particles)

Question 8

What makes a certain atom radioactive

Answer 8

when nuclei of it’s isotope unstable (these are called radioisotopes) The nucleus decays and emits radioactive gamma rays and/or subatomic particles of alpha or beta

Question 9

Theories of Light

Answer 9

light is electromagnetic radiations/waves that form a spectrum

Question 10

Hertz - photoelectric effect

Answer 10

electrons are emitted by matter that absorbs energy from shortwave electromagnetic radiation

Question 11

Planck

Answer 11

quantum hypothesis: showed that energy could be gained or lost in a quantum, as the temp of an object increases more of the large quanta of energy emitted and less of the smaller quanta of energy are emitted. The colour of light emitted by a hot object depends on the proportion of the quanra of different energies that are emitted

Question 12

quantum theory

Answer 12

an electron stays in plays because of electrostatic forces
if an electron absorbs a photon with the right quantity of enerfgy, the elctron can escape the metal surface
kinetic energy of the ejected electrons depends on the frequency of light being used
when the frequency is below a certain level, called the threshold frequency, no electrons are ejected

Question 13

Rutherford experiment

Answer 13

shot positivley charged alpha particles at thin sheet of gold foil, they should go straight through based on thomson’s model but did not (discovery of nucleus)

Question 14

isotopes

Answer 14

atoms with the same number of protons but different number of neutrons

Question 15

atomic number

Answer 15

the number of protons in a nucleus

Question 16

mass number

Answer 16

total number of protons and neutrons in a nucleus

Question 17

radioisotope

Answer 17

an isotope that emits radioactive gamma rays and/or subatomic particles (for example, alpha and/or beta particles)