Chapter 4: The Structure of the Atom Flashcards
Democritus
Coined term “atom”
John Dalton’s Atomic Theory
- Matter is made of tiny, chemically indestructible particles called atoms
- Atoms of the same element are identical in all ways*, atoms of different elements differ in all ways
- Elements may combine to form compounds
- In chemical reactions, elements combine in new ratios
* - False, should be number of protons
Subatomic Particles
Particles that make up atoms; smaller than atoms; discovered by experiments
Billiard Ball Model (Experimental Evidence, Characteristic, & Scientist)
No experimental evidence; Solid, homogenous sphere; John Dalton
Plum Pudding Model (Experimental Evidence, Characteristic, & Scientist)
Cathode ray tube; Chunks of electrons; J. J. Thompson
Planetary (Nuclear) Model (Experimental Evidence, Characteristic, & Scientist)
Gold foil experiment; Nucleus; Ernest Rutherford
Rutherford’s Observations And Conclusions
- Most particles passed directly through foil (Atoms are mostly empty space)
- Some particles bent to the side (The dense part of an atom has a positive charge)
- A few particles bounced backwards (There is a small, dense object in an atom)
Proton (Charge, Relative Mass, & Location)
Positive charge, 1 a.m.u. mass, Located in nucleus
Neutron (Charge, Relative Mass, & Location)
No charge, 1 a.m.u. mass, Located in nucleus
Electron (Charge, Relative Mass, & Location)
Negative charge, Negligible mass, Located in electron cloud
Standard Isotope Notation
Mass number in top left; Charge in top right; Atomic number in bottom left
Different Variations Of Atoms
Isotope - Mass differs due to different number of neutrons
Ions - Atoms with charges due to different number of electrons
Millikan Oil Drop Experiment
Found mass of electron
Rutherford’s 1919 Discovery
Discovered proton
Chadwick’s 1932 Discovery
Discovered neutron
Weighted Average Atomic Mass
Based upon masses of isotopes and their relative abundance
Radioactivity
Property of some unstable atoms that causes them to decay into different elements (transmutation)
Nuclear Radiation
Energy or particles given off during radioactive decay
Alpha Radiation (Nature, Relative Mass, Charge, & Stopped By…)
Helium nuclei (Helium-4 2+); Heaviest mass; Positive charge; Stopped by skin, paper, aluminium foil
Beta Radiation (Nature, Relative Mass, Charge, & Stopped By…)
Electrons; Light mass; Negative charge; Stopped by lead sheet (4 cm thick)
Gamma Radiation (Nature, Relative Mass, Charge, & Stopped By…)
Pure energy; No mass; No charge; Stopped by 1 m concrete
Conservation in Nuclear Equations
Atomic Mass Reactants = Atomic Mass Products
Atomic Number Reactants = Atomic Number Products
Nuclear Fission
Splits heavy element into fragments; used by nuclear reactors
Nuclear Fusion
Joins two light elements into heavier element; used in stars
Positron Emission
Some nuclei decay by emitting a positron, a particle that has the same mass as, but an opposite charge to, that of an electron
Electron Capture (K-Capture)
Addition of an electron to a proton in the nucleus (proton + electron = neutron)
Dominant Forms Of Decay
- Nuclei with more than 83 protons tend to decay by alpha emission
- Nuclei with too many neutrons tend to decay by beta emission
- Nuclei with too few neutrons tend to decay by positron emission or electron capture
Decay vs. Bombardment
Decay - Particle is product
Bombardment - Particle is reactant
Half Life
Time required for the radioactive decay of half the atoms in a sample
Half Life Equation
A(t)=O/[2^(t/h)]
A=final mass
t=time
O=original mass
h=half life
Carbon Dating
Measures the ratio of C-13 to C-12 to determine age of ancient materials
