Answer:
[tex]\% m/m=10.1\%[/tex]
Explanation:
Hello,
In this case given the molal solution of sucrose, we can assume there are 0.329 moles of sucrose in 1 kg of solvent, thus, computing both the mass of sucrose and solvent in grams, we obtain:
[tex]m_{sucrose}=0.329mol*\frac{342g}{1mol}=112.5g[/tex]
[tex]m_{solvent}=1000g[/tex]
In such a way, we proceed to the calculation of the mass percent as follows:
[tex]\% m/m=\frac{112.5g}{112.5g+1000g}*100\%\\ \\\% m/m=10.1\%[/tex]
Regards.
Question 1 (2 points) What are the three subatomic particles that make up an atom? Question 1 options: Nucleus, Electrons & Protons Protons, Electrons & Neutrons Protons, Neutrons & Nucleus Question 2 (1 point) Inside of the nucleus there are protons and neutrons. Question 2 options: True False Question 3 (1 point) Which statement below is true? Question 3 options: Neutrons are positive, Protons are negative, and Electrons are neutral Electrons are positive, Neutrons are negative, and Protons are neutral Protons are positive, Electrons are negative, and Neutrons are neutral Question 4 (1 point) The atomic number can tell us how many neutrons are in an atom. Question 4 options: True False Question 5 (2 points) The mass number is equal to which of the following? Question 5 options: Protons + Neutrons Protons + Atomic Number Neutrons + Electrons Protons - Neutrons Question 6 (1 point) In order to calculate how many neutrons are in an atom, you must subtract the mass number from the number of protons? Neutrons = Mass # - Protons Question 6 options: True False Question 7 (2 points) If I have an element with a mass of 56 and it has 26 protons, how many neutrons does it have? Question 7 options: 26 56 30 82 Question 8 (1 point) Isotopes are atoms with the SAME number of protons, but DIFFERENT numbers of neutrons. Question 8 options: True False Question 9 (3 points) Please have your periodic table of elements. An atom has 8 protons and 9 neutrons what is the chemical symbol for this isotope? Question 9 options: Flourine F-17 Oxygen O-17 Question 10 (2 points) How many protons and neutrons does iron-56 have? Question 10 options: 26 protons and 56 neutrons 26 protons and 26 neutrons 30 protons and 56 neutrons 26 protons and 30 neutrons
Answer:
1. electrons and neutrons protons
2. true
3. electrons are negative and neutrons are neutral
4. true
5. the total number of neutrons and protons
Explanation:
A student obtains a clean, dry graduated cylinder. She weighs the cylinder and finds the mass to be 32.64 g. She then fills the cylinder with a certain volume of water. She weighs the water-filled cylinder and finds the total mass to be 61.57 g. If the density of the water in the laboratory is 0.9975 g / mL , what is the volume of the water in the graduated cylinder?
Answer:
Explanation:
A student obtains a clean, dry graduated cylinder. She weighs the cylinder and finds the mass to be 32.64 g. She then fills the cylinder with a certain volume of water. She weighs the water-filled cylinder and finds the total mass to be 61.57 g. If the density of the water in the laboratory is 0.9975 g / mL , what is the volume of the water in the graduated cylinder?
Answer:
Volume of water =29.00mL
Explanation:
mass of cylinder (Mc)=32.64g
mass of water-filled cylinder (Mw+c)=61.57g
mass of water (Mw)= (Mw+c) - (Mc).
=(61.57 - 32.64)g = 28.93g
However:
Density = mass÷volume
hence Volume of water = mass of water÷density of water.
28.93g÷0.9975g/mL = 29.00mL
What causes the flame colors when salts are exposed to the flame? (hint: electrons jump
between different energy levels)
Answer:
When you heat an atom, some of its electrons are "excited* to higher energy levels. When an electron drops from one level to a lower energy level, it emits a quantum of energy. ... The different mix of energy differences for each atom produces different colours. Each metal gives a characteristic flame emission spectrum.
Explanation:
Explain the significance of:_______. a) a very large value of K, b) a very small value of K, and c) a K value of about 1.0.
Answer:
See explanation
Explanation:
a) A large value of K shows that the reaction is product favoured. It implies that more reactants are converted to products and the equilibrium concentration of products in the system is far higher than that of the reactants. The reaction will proceed towards the right hand side.
b)A small value of K implies that the reaction is reactant favoured. There are more reactants than products present at equilibrium and the reaction will proceed towards the lefthand side.
c) K=1 implies the presence of a significant concentration of reactants and products in the system at equilibrium.
if a=b, what is the numerical value of the quantity a/b?
Answer:
The numeric value is 1.
Explanation:
We have given that the “a” equal to “b” which means we can replace the “a” with “b” or we can replace the “b” with “a”.
The given condition or quantity = a/b.
Now it is required to find the numeric value of a/b.
To find the numeric value we first replace the “b” with “a” and then divide the values. Since we know that if the numeration and denominators are the same then after dividing the value, the resulting value will be 1.
The numerical value = a/b = a/a = 1
An unknown element X has the following isotopes: ²⁵X (80.5% abundant) and ²⁷X (19.5% abundant). What is the Average atomic mass in amu of X?
Answer:
the average atomic mass in amu of X is 25.39 amu
Explanation:
The computation of the average atomic mass in the amu of X is shown below:
Average mass is
= Product sum + atomic mass of each and every isotope
Now the average mass
= (80.5 ÷ 100 × 25 amu) + (19.5 ÷ 100 × 27 amu)
= 20.125 + 5.265
= 25.39 amu
Hence, the average atomic mass in amu of X is 25.39 amu
The average atomic mass of X is 25.39 amu.
Atomic massIt is the quantity of matter present within an atom of an element.
Based on the given information,
• The unknown element X has the isotopes, 25X (80.5% abundant) and 27X (19.5% abundant).
Now the atomic mass of X can be calculated by using the formula,
[tex]=\frac{(M1*A1)+(M2*A2)}{A1+A2}[/tex]
Here, M1 and M2 are the atomic masses, and A1 and A2 are their abundances.
Now putting the values we get,
[tex]= \frac{(25*80.5)+(27*19.5)}{80.5+19.5} \\\\= \frac{2012.5+526.5}{100} \\= \frac{2539}{100} \\= 25.39 amu[/tex]
Thus, the average atomic mass of X is 25.39 amu.
For more information about atomic mass see here :
https://brainly.com/question/20885284
What is chemistry?
A. The scientific study of matter
B. The study of living things
C. The study of how matter and energy interact
D. The study of changing ideas
Answer:
the scientific study of matter i believe
Explanation:
because the definition says the branch of science that deals with the identification of the substances of which matter is composed
Which of the following is the conjugate acid of water?
Answer:
Hydronium ion
The conjugate acid of water is the hydronium ion ; [tex]H_3O^+,[/tex]
Explanation:
It is an ion formed by the association of a hydrogen ion with a water molecule.
Katrina is investigating the properties of volume for the different states of matter. First, she places a cube in a bowl of water and observes what happens. Next, she takes the cube out of the water and pours the water into a glass. Which statement describes the observations Katrina made? A. When the cube was placed in the water, the volume and shape stayed the same. When the liquid was poured from the bowl, the shape changed. B. When the cube was placed in the water, the volume of the water changed. When the liquid was poured from the bowl, the shape changed. C. The volume of the cube and the water changed when the cube was placed into the water. The volume of the liquid changed when it was poured out of the bowl. D. The shape and volume of the cube and the liquid changed when the cube was placed in the bowl. The liquid stayed the same when it was poured from the bowl.
Answer:
When the cube was placed in the water, the volume of the water changed. When the liquid was poured from the bowl, the shape changed.
Explanation:
When a cube is placed inside water, the volume of the water will change due to the introduction of the cube as the cube will displace some water. Remember that the shape of a liquid is the shape of its container so the shape of the water remains the same.
When the water is poured into a glass, its shape changes as it now assumes the shape of the glass as explained above.
Answer: When the cube was placed in the water, the shape of the cube stays the same. When the liquid was poured from the bowl into the glass, the shape changed
Explanation:
Data Tables Practices
Table 1 Information: Allison wanted to find out if the color of soda affected whether her friends would
choose a particular one. She collected the following data:
Orange Soda - 5 friends
Yellow Soda - 7 friends
Green Soda - 2 friends
Clear Soda - 1 friend
Brown Soda - 15 friends
Table 1 Title:
Independent Variable:
Dependent Variable:
Make a data table in this space, include labels for variables and the title:
Page
2
+
/ 5
Answer:
Title: Effect of soda color on the choice of Allison's friends.
Independent variable: Color of Soda
Dependent variable: Friends' choice/Number of friends that chose a particular soda
Please find the data table attached as an image.
Explanation:
A data table is used to organize the data recorded after an experiment. The data table shows the title of the experiment, which is written directly above the table. It also shows the independent variable (on the first column) and the dependent variable (on other columns to the right).
- In this experiment, the title of the data table can be written as EFFECT OF COLOR OF SODA ON THE CHOICE OF ALLISON'S FRIENDS.
- The independent variable is the manipulated or changed variable, which is the COLOR OF SODA in this case.
- The dependent variable is the variable that is measured in an experiment, which is the NUMBER OF FRIENDS THAT CHOSE EACH SODA in this case.
Alexander is measuring the width of objects. The smallest measurement his ruler displays is centimeters. Rather than
rounding to one significant figure beyond what he can measure with certainty, he rounds his data to the nearest centimeter to
make his math easier. Enter the amount of uncertainty that is created by this rounding error.
Answer:
There can be error in millimetres.
Explanation:
The rounding off can create errors in exact measurement. There can be errors in the measured value and actual measurement of the object. Alexander has rounded his calculation to nearest centimetre then it is possible he can make errors in millimetre calculations. The measured width of the object will not be the actual measurement and it might differ slightly.
How is energy transformed from one form to another? Give three examples of objects that have potential energy and kinetic energy? What does the law of convosation of energy state? .
Answer:
An energy transformation is the change of energy from one form to another. Energy transformations occur everywhere every second of the day. There are many different forms of energy such as electrical, thermal, nuclear, mechanical, electromagnetic, sound, and chemical.
Explanation:
Rank the following compounds from least acidic(rank 1) to most.A. AcetaldehydeB. Methyl acetate.C. N,N-dimethylacetamide1. least acidic2. most acid
Answer:
N,N-dimethylacetamide < Methyl acetate < Acetaldehyde
Acetaldehyde - least acidic
Methyl acetate - acidic
N,N-dimethylacetamide - most acidic
Explanation:
The order of acidity of the organic compound under study is primarily influenced by their resonance effect. The resonance effect explains how polar a particular molecule is from the interaction between pi -bonds or a lone electron pair and a pi-bond in a molecule.
In acetaldehyde popularly known as ethanal, the CH₃CHO functional group -CHO is attached to an adjacent end of the compound, which has a lesser resonance effect than methyl acetate.
Methyl acetate, also known as methyl ethanoate, is an ester family with the formula CH₃COOCH₃ is also lesser in its acidity compared to N,N-dimethylacetamide.
Therefore, the order of acidity from the least acidic to the most is:
N,N-dimethylacetamide < Methyl acetate < Acetaldehyde
Acetaldehyde - least acidic
Methyl acetate - acidic
N,N-dimethylacetamide - most acidic
Look at the image below:
Which of the following statements is true?
Group of answer choices
The figure is a molecule and a compound.
The figure is a compound, but not a molecule.
The figure is an atom and an element.
The figure is a molecule and an element.
Answer:
The figure is a molecule and a compound
Explanation:
Because it have 2 cluster molecules
What is the density of a copper blocks if it has a mass of 43.5 grams and a volume of 4.85 cm^3?
One way to represent this equilibrium is: 2 CO2(g) + 4 H2O(g)2 CH3OH(l) + 3 O2(g) We could also write this reaction three other ways, listed below. The equilibrium constants for all of the reactions are related. Write the equilibrium constant for each new reaction in terms of K, the equilibrium constant for the reaction above. 1) CH3OH(l) + 3/2 O2(g) CO2(g) + 2 H2O(g) K1 = 2) 2 CH3OH(l) + 3 O2(g) 2 CO2(g) + 4 H2O(g) K2 = 3) CO2(g) + 2 H2O(g) CH3OH(l) + 3/2 O2(g)
Answer:
1) 1/√K
2) 1/K
3) √K
Explanation:
As general rules of operation of equilibrium constants:
For the reaction:
A + B ⇄ C + D; Equilibrium constant = K
C + D ⇄ A + B; K' = 1/K
2A + 2B ⇄ 2C + 2D; K'' = K²
Thus, as equilibrium constant of:
2CO2 + 4H2O ⇄ 2CH3OH + 3O2
Is K:
1) CH3OH + 3/2 O2 ⇄ CO2 + 2H2O
K' = 1 / K^(1/2) = 1/√K
2) 2CH3OH + 3O2 ⇄ 2CO2 + 4H2O
K' = 1/K
3) CO2 + 2H2O ⇄ CH3OH + 3/2 O2
K' = K^(1/2) = √K
Which species is oxidized in the following reaction? CO2 + H2 → CO + H2O A. H B. CO2 C. C D. O
it should be option A. H
[ because H gained oxygen ( O ) ]
Oxidation is defined by :
- the loss of electrons
- the loss of hydrogen ( H )
- the gain of oxygen ( O )
- increase in oxidation state
Reduction is defined by :
- the gain of electrons
- the gain of hydrogen ( H )
- the loss of oxygen ( O )
- decrease in oxidation state
(Basically, oxidation n reduction is opposite of each other)
The species being oxidized in the following reaction is Carbon Dioxide (CO2). This can be determined by looking at the oxidation states of the reactants and products.
What happens in case of reactants ?In the reactants, Carbon Dioxide (CO2) has an oxidation state of +4, while Hydrogen (H2) has an oxidation state of 0. In the products, Carbon (CO) has an oxidation state of +2, and Water (H2O) has an oxidation state of -2.
The net change in oxidation states between the reactants and products is a decrease of 6, which means that the species that was being oxidized is Carbon Dioxide (CO2). The oxidation state of a species can be determined by looking at the number of electrons it has gained or lost in a reaction.
In this reaction, Carbon Dioxide (CO2) has lost 6 electrons, which is a sign that it is the species being oxidized. This is further evidenced by the fact that Carbon (CO) and Water (H2O) have gained electrons, meaning that they are the species being reduced. Therefore, the species being oxidized in the following reaction is Carbon Dioxide (CO2).
Learn more about Carbon Dioxide at:
https://brainly.com/question/3049557
#SPJ3
Use a volumetric flask to prepare 100.00 mL of 0.70M HCl solution. Do this by diluting either one of the stock hydrochloric acid solutions that have been set out for you to use (the stock solutions are 3.0M and 6.0M HCl). (WARNING! Concentrated HCl is caustic and will cause burns. Handle carefully.) Dispose of any excess HCl in the waste container.
Answer:
- Take 3.3 mL of 3.0-M hydrochloric acid and subsequently add 76.7 mL of water to complete the 100.00 mL.
- Take 11.7mL of 6.0-M hydrochloric acid and subsequently add 88.3 mL of water to complete the 100.00 mL
Explanation:
Hello,
In this case, given that the dilutions are preparedfrom 3.0-M and 6.0-M hydrochloric acid, we must proceed as follows:
- 3.0-M stock: when using this stock, the aliquot you must take is computed as shown below:
[tex]V_1=\frac{M_2V_2}{M_1}=\frac{100.00mL*0.70M}{3.0M}=23.3mL[/tex]
It means that you must take 23.3 mL of 3.0-M hydrochloric acid and subsequently add 76.7 mL of water to complete the 100.00 mL.
- 6.0-M stock: when using this stock, the aliquot you must take is computed as shown below:
[tex]V_1=\frac{M_2V_2}{M_1}=\frac{100.00mL*0.70M}{6.0M}=11.7mL[/tex]
It means that you must take 11.7mL of 6.0-M hydrochloric acid and subsequently add 88.3 mL of water to complete the 100.00 mL.
Regards.
A chemist measures the energy change ?H during the following reaction: 2HgO (s) ?2Hg (l) +O2 (g) =?H182.kJ Use the information to answer the following questions. This reaction is...
endothermic.
exothermic.
Suppose 72.8g of HgO react. Will any heat be released or absorbed?
Yes, absorbed.
Yes, released.
No.
If you said heat will be released or absorbed in the second part of this question, calculate how much heat will be released or absorbed. kJ Round your answer to 3 significant digits. ×10
Answer:
The reaction is endothermic.
Yes, absorbed
3.06x10¹kJ are absorbed
Explanation:
In the reaction:
2HgO(s) → 2Hg(l) + O₂(g) ΔH = 182kJ
As ΔH >0,
The reaction is endothermic
As the reaction is endothermic, when the reaction occurs,
the heat is absorbed.
Now, based on the equation, when 2 moles of HgO (Molar mass: 216.59g/mol), 182kJ are absorbed.
72.8g are:
72.8g * (1mol / 216.59g) = 0.3361 moles HgO.
that absorb:
0.3361 moles HgO * (182kJ / 2 moles) =
3.06x10¹kJ are absorbedwhich of the following is NOT a chemical property?
Conductivity
Malleability
Reactivity
Freezing
Answer:
Malleability
Explanation:
Answer:
Malleability is not chemical property
Convert 533 cm/s to units of meters per minute. Show the unit analysis by dragging the conversion factors into the unit‑factor slots
Answer:
319.8 m/min
Explanation:
533 cm/s
We can convert 533 cm/s to m/min by doing the following:
First, we shall convert 533 cm/s to m/s. This can be obtained as illustrated below:
Recall:
100 cm/s = 1 m/s
Therefore,
533 cm/s = 533 cm/s /100 cm/s × 1 m/s
533 cm/s = 5.33 m/s
Finally, we shall convert 5.33 m/s to m/min. This can be obtained as follow:
1 m/s = 60 m/min
Therefore,
5.33 m/s = 5.33 m/s / 1 m/s × 60 m/min
5.33 m/s = 319.8 m/min
Therefore, 533 cm/s is equivalent to 319.8 m/min
What is the density of an object that has a mass of 6.5 g and when placed in water displaces the volume from 4.5mL to 11.8mL? round to the nearest tenth
Answer:
[tex]\rho =0.9g/mL[/tex]
Explanation:
Hello,
In this case, due to the volume displacement caused the by the object's submersion, it's volume is:
[tex]V=11.8mL-4.5mL=7.3 mL[/tex]
In such a way, considering the mathematical definition of density, it turns out:
[tex]\rho =\frac{m}{V}=\frac{6.5g}{7.3mL}\\ \\\rho =0.89g/mL[/tex]
Rounding to the nearest tenth we finally obtain:
[tex]\rho =0.9g/mL[/tex]
Regards.
There are liquids of different densities together in a container. What will happen to the liquid with the lowest density? Answers: A)It will move to the bottom. B)It will move to the top. C)It will bubble out as a gas. D)It will form a solid.
Answer:
b
Explanation:
6. The SI unit of weight is a newton (N). If a boulder weighs 240 N
on Earth, what is its weight on the moon?
a 40N
b 60 N
C 240 N
d 120 N
Answer:
A. 40N
Explanation:
(The radioisotope 224Ra decays by alpha emission via two paths to the ground state of its daughter 94% probability of alpha decay directly to the daughter ground state;(20 pts, 5 pts each)5.5% probability of alpha decay to an excited state before emitting a 0.241 MeV photon in an isomeric transition to reach the ground state of the daughter.a.Write the reaction equation for the alpha decay of 224Ra. b.Calculate the Q-value (in MeV) of this reaction. c.What are the energies (in MeV) of the two associated alpha particles? d.Sketch the decay scheme for the decay of 224Ra with the associated probabilities, energies, and emissions for the a
Answer:
a) ²²⁴Ra₈₈ ---> α + ²²⁰Rn₈₆ + Q
b) the Q-value of this reaction is 5.789 MeV
c) the energies (in MeV) of the two associated alpha particles are; 5.69 MeV and 5.449 Mev
Explanation:
a)
The decay equation for the alpha decay is expressed as;
²²⁴Ra₈₈ ---> α + ²²⁰Rn₈₆ + Q
b)
Calculate the Q-value (in MeV) of this reaction.
Q = Mparent - Mdaughter -Mg
Q = MRa - MRn -Mg
= 224.020202 - 220.011384 - 4.00260305
= 0.00621495 amu
= 5.789 MeV
therefore the Q-value of this reaction is 5.789 MeV
c)
Energy of alpha particle is expressed as;
E∝ = MQ / ( m + M)
now this is the maximum energy available for the daughter, ²²⁰Rn going to the ground state;
The energy of the alpha particle gives;
E∝ = 220(5.789) / ( 4 + 220) = 5.69 MeV
as given in the question,The other less frequent alpha occurring 5.5% of the time leaves the daughter nucleus in an excited state of 0.241 MeV above the ground state.
Therefore the energy of this alpha is
E∝ = 5.69 - 0.241 = 5.449 Mev
Therefore the energies (in MeV) of the two associated alpha particles are; 5.69 MeV and 5.449 Mev
d)
Sketch of the nuclear decay scheme have been uploaded along side this answer.
(a)[tex]^{224}Ra_{_{88}}=^4\alpha_{_2}+^{220}Rn_{_{86}}+Q[/tex]
(b) the Q-value of the reaction is 5.789 MeV
(c) The alpha particles have energies of 5.69 MeV and 5.449 MeV
Alpha decay:(a) The alpha decay of the radioisotope 224Ra is given by:
[tex]^{224}Ra_{_{88}}=^4\alpha_{_2}+^{220}Rn_{_{86}}+Q[/tex]
(b) The Q-value of a reaction is given by:
Q = {mas of reactants - mass of products}c²
[tex]Q = [M_{224Ra} - M_{\alpha} - M_{220Rn}]c^2[/tex]
Q = (224.020202 - 220.011384 - 4.00260305) amu.c²
Q = 0.00621495 × 931.5 MeV ( since 1 amu.c² = 931.5 MeV)
Q = 5.789 MeV
(c) The energy of the alpha particle is expressed as;
E(α) = MQ / ( m + M)
it is the maximum energy available for the daughter nucleus, ²²⁰Rn going to the ground state.
If the daughter nucleus is at rest then all the energy is carried by the alpha particle.
The energy of the alpha particle is:
E(α) = 220(5.789) / ( 4 + 220) = 5.69 MeV
Now, for the alpha particle occurring 5.5% of the time and leaving the daughter nucleus in an excited state of 0.241 MeV :
The energy of this alpha particle is
E(α) = 5.69 - 0.241 = 5.449 Mev
Learn more about alpha decay:
https://brainly.com/question/2600896?referrer=searchResults
If you burn yourself in lab you should?
A. See the nurse after class
B. Tell the instructor
C. See a doctor after school
D. Apply first aid yourself
Answer:
B. Tell the instructor
Explanation:
Always to the instructor about any accidents happens in a lab.
Answer:
B
Explanation:
Just helping out:)
Three blocks of the same mass are placed in front of you. Block A has a volume of
3.0 cm", block B of 5.0 cm', and block C of 10.0 cm. Which has the higher
density?
Given :
Three block of same mass name A , B and C .
Sides of block A , B and C is 3.0 cm , 5.0 cm and 10.0 cm .
To Find :
Which block has the higher density .
Solution :
We know , density [tex]\rho[/tex] is given by :
[tex]\rho=\dfrac{M}{V}[/tex] ......1 )
Here , V is volume .
Now , volume V for cube is given :
[tex]V=a^3[/tex] .......2 )
( Here , a is the side of cube )
Now ,form equation 1 we can see if mass remains constant then density decrease with increase in volume.
Therefore , cube with minimum side will have higher density , in this case it is 3 cm block .
Hence , this is the required solution .
What is the name of the binary molecule H2O2? This compound is also known as hydrogen peroxide and is a properly disinfectant or cuts and scrapes.
Answer:
hydrogen dioxide
Explanation:
Hydrogen dioxide is the name of the binary molecule H2O2 ,therefore option (b) is correct from the image below.
What do you mean by hydrogen dioxide ?A thick, colorless liquid, H2O2, resembling water, but having a bitter, sour taste, produced by the action of acids on barium peroxide.
It decomposes into water and oxygen, and is manufactured in large quantities for an oxidizing and bleaching agent. Called also oxygenated water.
A colorless, unstable compound of hydrogen and oxygen (H 2 O 2). It is used as an antiseptic and bleaching agent.
Hydrogen dioxide is the name of the binary molecule H2O2 ,hence option (b) is correct from the image below.
Learn more about hydrogen dioxide, here:
https://brainly.com/question/10140462
#SPJ2
chemistry screen shot below plzzzzzzz help i've been stuck forever
Answer:
True
Explanation: Imagine the Electrons is by the nucleus which give more energy.
Blue light waves have more energy than red light waves. Which of these situations most likely produces a photoelectric effect? You may assume that the same metal is used in each situation.
Answer:
You may assume that the same metal is used in each situation. Light is emitted by electrons when they drop from one energy level to a lower level.