S1.2 (Nuclear Atom)

Question 1

Daltons theory

Answer 1

• elements contain tiny particles called atoms
• atoms can combine to form compounds
• atoms cannot be created, detsroyed or divided

Question 2

Thompson’s Theory

Answer 2

• plum-pudding model
• negative charges are held by positively charged ball
• discovered by cathode ray

Question 3

Rutherfords Theory

Answer 3

• atoms are mostly empty space
• proved by gold foil experiment

Question 4

Gold foil experiment

Answer 4

1. alpha particles are ried at thin gold foil sheet
2. most alpha particles are undeflected & hit circular fluorescent screen coated in zinc sulfide (creates flash of light so you know they were undeflected)
3. small number of helium atoms were deflected as they hit the nucleus (+ with +) = meant there was a strong positive core

=> proved that atoms were mostly empty space

Question 5

Planetary model

Answer 5

(differently orientated ringed one with nucleus inside)
* atoms mass and positive charge is condensed in tiny core
* electrons circulate it

Question 6

Isotopes

Answer 6

Atoms of the same element with a different number of protons but the same number of neutrons

Question 7

Properties of Isotopes

Answer 7

Isotopes have the same chemical properties as its original element as they electrons do not change

Question 8

RAM Formula

RAM = Relative Atomic Mass

Answer 8

∑Isotope abundace x Isotope Mass/Isotope Abundance

Question 9

Mass spectronomer

Answer 9

Instrument that seperates particles based on their mass to charge ratio (m/z) and measures masses of isotopes as well as isotope abundance (%)

Question 10

How a mass spectronomer works to give us a graph with peaks

Answer 10

1. makes the species have a 1+ charge which allows to calculate the mass
2. can detect ions, whole molecules, molecular ions, molecular fragments

Question 11

Mass spectra of diatomic molecules

Answer 11

• shows intensity relative to most abundant molecule
• consider the fact that there are multiple ion combinations (ex. 35CL37CL+)

Question 12

How do isotopes differ in chemical properties

Answer 12

They do not as only neutrons differ in isotopes and the chemical properties are determined by electrons

Question 13

Why radioactive isotopes are bad

Answer 13

They emit radiation which can be damaging to cells

Question 14

Half life equation

Answer 14

Initial substance x 0.5 to the power of amount of half lifes

Question 15

Hoe you know which ions will be deflected the most in a mass spectronomer

Answer 15

• lighter ions
• higher charged ions