Atoms & Isotopes

Question 1

Atoms

Answer 1

Positively charged nucleus (contains most of atom mass), surrounded by negatively charged electrons

Question 2

Atom Size

Answer 2

Radius of atom: 1x10-10m
Radius of nucleus: 1/10,000 of atom

Question 3

Energy Levels

Answer 3

Energy levels further from nucleus have more energy
If atoms absorbs EM radiation (gain energy), electron moves to higher energy level
If atom emits EM radiation (loses energy), electron moves to lower energy level

Question 4

Mass number & Atomic number

Answer 4

Number of electrons = number of protons in nucleus. Atoms have no overall electrical charge
Atoms of same element have same number of protons

Question 5

Isotopes

Answer 5

Atoms of same element with different number of neutrons

Question 6

Ions

Answer 6

Atoms turn into positive ions if they lose one or more outer electrons, negative if they gain electrons

Question 7

History of Atom

Answer 7

Solid spheres - John Dalton - Billiard ball model
Discovery of electron - J. Thompson - Plum pudding model
Alpha scattering - Rutherford - Nuclear model
Electrons orbit nucleus in energy levels at specific distances - Bohr
Protons make up nucleus - Rutherford
Neutrons also make up nucleus - Chadwick

Question 8

Alpha scattering experiment

Answer 8

Atom is mostly empty space (most alpha particles went straight through)
Centre of atom is positively charged (some alpha particles were deflected)
Mass of atom concentrated in tiny nucleus (some alpha particles repelled back