Standard 2 1. energy changes in the atom specific to the movement of electrons between energy levels...
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Transcript of Standard 2 1. energy changes in the atom specific to the movement of electrons between energy levels...
Standard 2 1. energy changes in the atom specific to the movement of electrons between energy levels in an atom resulting in the
emission or absorption of quantum energy. 2. emission of high-energy particles results from nuclear
changes 3. that matter can be converted to energy during nuclear
reactions.
2.1
Evaluate quantum energy changes in the atom in terms of the energy
contained in light emissions.
• A. What is the relationship between wavelength and energy? What would the graph look like?
• Increase - Decrease
Visible light • least Energy and the longest wavelength?• Red• Most Energy and the shortest wavelength?• Violet
Hint:ROYGBIV
Hint:ROYGBIV
ROY GIV
• Red = lower energy because Roy is a lazy boy
• Violet = higher energy
• Remember energy and wavelength are opposites.
b. Lab evidence energy, electrons and energy levels?
• What happens to an electron when it is excited?
• It jumps to a higher energy level – absorbing a quanta (amount) of energy.
• What happens when it falls back down to its ground state?
• It emits light of a specific wavelength (color)
• When elements are heated or electrically excited, they may give a line spectrum.
• They absorb only certain amounts of energy, or quanta. Then energy as the electron falls back down.
Each element has its own set of lines. Analyzing lines from distant stars tell us what elements are present in the star.
• The reason that the images are lines is that the light from the lamp is focused on a narrow slit. The illustration shows the separation of a light beam into its component colors
Unknown
Flame test
• Works in the same way to identify some elements.
Barium Calcium Sodium RubidiumWhat is the unknown?
Put these in order from lowest to highest Energy.
2.2
Nuclear Reactions
Changes in the nucleus of an atom result in emission of radioactivity. --
Radioactive means unstable
Can matter be converted to energy?
• Yes but only in nuclear reactions
Fission Reactions
• Fission occurs when atoms split, ex nuclear bombs.
Fusion reactions
• Fusion occurs when atoms combine to form bigger atoms. Ex. hydrogen turns into helium in the sun.
Elements with unstable nucleus will become stable by emitting?
• Particles – The most common are are α, β and γ.
alpha (helium nucleus) emission:
• U⟶He + Th (stopped by paper)
beta (electron) emission
• C N + ⟶ e
gamma emission:
• Tc-m Tc + ⟶ γ (stopped by lead)
Put in order of mass. From least to greatest.
Gama y Beta , Alpha ,
Hint: – Alpha is a Helium, Beta is an electron
Put in order of penetrating power. From least to greatest.
Alpha , Beta , Gama y
Hint: – Alpha is a Helium, Beta is an electron
Put in order of Energy . From least to greatest.
Alpha , Beta , Gama y
Hint: – Alpha is a Helium, Beta is an electron
Same as penetrating power
2.2.3 Symbol
Actual
Mass
Penetrating Power
Energy
α 4 Little (Paper stops)
Low
β ~0 Medium
Medium
γ 0 High (5 ft concrete)
Very High
What are the effects of radiation?
Good Bad
Radioactive – the good
• Tracer - To identify and diagnose
• The medicine, iodine 131, is a proven cancer fighter.
• But it's also radioactive, and in higher doses, can cause cancer
What are the dangers of radiation?
• small doses may burn tissue, disable cell division and the immune system.
Small doses over time may cause cancer and genetic defects.
Large doses• Death from radiation
sickness is often by dehydration because the digestive tract is damaged.
Marie Curie
• Discovered radiation but eventually died from it.
Turtles exposed to radiation
What is the difference between nuclear reactions and chemical
reactions?• Nuclear reactions involve changes in the
nucleus.• Chemical reactions involve valence (outer shell
electrons.
What is the difference between Energy produced in nuclear
reactions and chemical reactions?• Nuclear Reactions produces much higher
amounts of energy
What is half life?
• The time it takes for half of an unstable element to decay.
• How do we use this?• To determine the age of a substance –
radiometric/ radioactive or carbon dating
What is the concentration at 200 years?
•
• How many years old is this when 20 % of the strontium is left?