An entire group of elements was unknown when the periodic table was first developed because they were unreactive and no known compounds were composed of them.

What most likely led to the inclusion of these elements in the periodic table?
the formation of a compound in the laboratory
new technology that showed how to identify one of the elements
improvements in instruments to measure small masses
more careful experiments to create synthetic elements

Answer:

2.4×1024 atoms.

Explanation:

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However, keep in mind that 20 mSv per year is the recommended amount for any radiation worker and is still regarded quite safe. This is the most radiation most of us will ever be exposed to.

after 1st half life , remaining sample would be 100/2=50 g

after 2nd half life , remaining sample would be 50/2=25 g

after 3rd half life , remaining sample would be 25/2= 12.5 g

The half-life of a radionuclide is the amount of time it takes for half of its radioactive atoms to decay. A decent rule of thumb is that you will have less than 1% of the initial quantity of radiation after seven half-lives. Click here to learn more about half life.

A short-term and whole-body dosage would result in rapid sickness, such as nausea and a reduction in white blood cell count, followed by death.

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42.08 years of  time must pass before there is an acceptable radiation level at the site.​

What is the half-life of a radioactive material?

The half life of a radioactive substance is the period of time during which its mass or number of atoms is decreased to half of what it was initially. The time it takes for a radioactive substance (or half of its atoms) to break down or transform into another substance is commonly used to define half-life.

Radioactivity, as its name suggests, is the act of generating radiation without any external cause. This is accomplished by an atomic nucleus that is unstable for whatever reason and "wants" to surrender some energy in order to change its configuration to one that is more stable.

After first half-life will remain 2560/2 i.e. 1280g of radioactive substance.

After second half-life will remain 1280/2 i.e. 640g

After 3rd half-life will remain 640/2 i.e. 320g

After 4th half-life will remain 160g

After 5th half-life will remain 80g

After 6th, 7th and 8th half-life will remain 40g, 20g and 10g respectively

It takes 8 half-lives to reach acceptable level of radiation i.e. 8*5.26 years

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Yes, the presence of a material can cause a pure solvent (like water) to have a lower freezing point and a higher melting point. Both freezing point depression and melting point elevation are terms used to describe this occurrence.

Liquid molecules are weakly bonded, and their intermolecular forces of attraction are weaker than those of solid molecules.

This is because the molecules' potential energy, which holds them together in the crystal lattice of a solid, is smaller than the heat energy that is delivered to them during the process of changing from a solid to a liquid state.

This potential energy serves as a proxy for the solid's lattice energy.

The molecules lose their kinetic energy and approach one another when the temperature of a substance is lowered through the removal of heat from the substance or a reduction in pressure.

They gradually build more potential energy and stabilize. They turn into solids at this point. It's one of the reliable

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Coal combustion produces more greenhouse gases than the combustion of any other fossil fuel

Explanation:

There are a handful of coal types, but almost all contribute substantially more CO2 into the air than other fossil fuels upon combustion.

Answer:

thermal decomposition

Diverticular disease is a common condition among adults over the age of 40 in the United States. Studies suggest that between 10% to 40% of U.S. adults over 40 have diverticular disease. This condition occurs when small, bulging pouches (diverticula) develop in the lining of the digestive system, most commonly in the large intestine.

Symptoms of diverticular disease can vary, but roughly 15% to 25% of individuals with diverticular disease show signs and symptoms of the disease, which may include abdominal pain, bloating, constipation, and diarrhea. The likelihood of developing diverticular disease increases with age, and the percentage of U.S. adults having the disease jumps to 50% by the age of 60. Other risk factors for developing diverticular disease include a diet low in fiber, obesity, smoking, lack of physical activity, and certain medications.

If left untreated, diverticular disease can lead to complications such as infections, bleeding, and perforations in the intestinal wall. Therefore, it is important to seek medical attention if you experience any symptoms of diverticular disease. Treatment may include dietary changes, medication, and, in severe cases, surgery.

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Explanation:

Hello mr/mrs (name) I unfortunately couldn't pay attention to the class due to some issues I had therefore I don't know what we are doing in class

OR

Hello mr/mrs (name) I could understand what we were doing in class I would like it if you could break it down more or explain better to me

OR just say something it had something to do with your internet such as

Hello mr/mrs (name) I didn't understand what you were saying during our class due to some of my internet issues I was have throughout the day. I hope you can explain what we did during the class.

Those may be some of my excuses I've used before

they have worked for me:)

I don't know if that helped?:/

The mass of NaCl added in 100 gm of water (Kb​=0.51K kg mol−3) to make its boiling point at 100∘C is: Option a. 10.68 g.

To determine the mass of NaCl needed to make the boiling point of water at 100°C given the boiling point at 735 torr is 99°C, we'll use the molality equation and the colligative property of boiling point elevation. The given terms are boiling point, torr, NaCl, mass, water, and Kb.

1. Calculate the boiling point elevation, ΔTb:
ΔTb = T_final - T_initial
ΔTb = 100°C - 99°C
ΔTb = 1°C

2. Use the boiling point elevation equation:
ΔTb = Kb * molality

3. Rearrange the equation to find molality:
molality = ΔTb / Kb
molality = 1°C / 0.51 K kg mol⁻³
molality = 1.96 mol/kg

4. Calculate the moles of NaCl:
moles of NaCl = molality * mass of solvent (water) / 1000
moles of NaCl = 1.96 mol/kg * 100 g / 1000
moles of NaCl = 0.196 mol

5. Calculate the mass of NaCl using its molar mass (58.44 g/mol):
mass of NaCl = moles of NaCl * molar mass
mass of NaCl = 0.196 mol * 58.44 g/mol
mass of NaCl = 11.44 g

The closest answer to the calculated value is 10.68 g, so the correct option is:
a. 10.68 g.

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Answer:

1.heterogeneous mixture

2.element

3.compound

4.homogeneous mixture

Explanation:

The correct pairs are:

A cloud, which consist of small water droplets - Heterogeneous mixture

Distributed throughout the air

helium, a gas composed of identical atoms - Element

Rubbing alcohol, a liquid composed of chemically bonded - Compound

Carbon, Oxygen, and Hydrogen atoms

sugar thoroughly dissolved in water - Homogenous mixture.

In Heterogenous mixture, the composition of the mixture is not uniform. In Homogenous mixture, the composition is uniform throughout. Element is the combination of same atoms. Compound contains two or more elements.

Therefore, the correct pairs are,

A cloud, which consist of small water droplets - Heterogeneous mixture

Distributed throughout the air

helium, a gas composed of identical atoms - Element

Rubbing alcohol, a liquid composed of chemically bonded - Compound

Carbon, Oxygen, and Hydrogen atoms

sugar thoroughly dissolved in water - Homogenous mixture.

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Answer:

Hydrogen bonding is the major intermolecular attraction responsible for the relatively high boiling points of alcohols.

Answer: Yttruim: 39 protons, 50 neutrons, 39 electrons

Ruthenium: 44 protons, 57 neutrons, 44 electrons

Place the atomic number subscript and mass number superscript to the left of the atomic symbol.

The chemical properties of an atom are determined by its atomic number and are represented by the symbol Z. The total number of nucleons in an atom is the atomic mass number. This value is represented by the symbol A.

Isotopes are members of a family of elements that have the same number of protons and a different number of neutrons. The number of protons in the nucleus determines the atomic number of an element on the periodic table. Isotopes are atoms of the same element that contain the same number of protons but different numbers of neutrons.

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The IUPAC International Union of Pure and Applied Chemistry (IUPAC) name for the following compound is 4-hydroxy-2-pentanone.

The International Union of Pure and Applied Chemistry (IUPAC) is a scientific organization in charge of developing and improving chemical nomenclature, symbols, and terminology, as well as teaching the world about chemistry.

Therefore, the IUPAC name for the given compound is 4-hydroxy-2-pentanone.

Option A, 4-hydroxy-2-pentanone, is the correct answer as it follows the correct order of numbering and name formation.

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The correct answer is equality which tells how much of one unit is equal to another unit.

By determining the base quantities and units of measure for each physical quantity and tracking these dimensions as computations or comparisons are made, the dimensional analysis examines the relationships between various physical quantities. Due to the regular 10-base in all units, converting between dimensional units within the metric or SI system is frequently simpler than it is in other systems. Algebraic conversions are frequently done using dimensional analysis, most specifically the factor-label approach also called the unit-factor method. Even if they are initially expressed in different units of measure, such as yards and meters, commensurable physical quantities are the same kind, have the same dimension, and may be compared directly to one another.

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Answer:

A

Explanation:

Answer:

A! have a wonderful day!

Explanation:

Answer:

Liquid A is a homogeneous mixture and Liquid B is a heterogeneous mixture

Explanation:

'Liquid' is characterized as 'a substance that is flowing and does not carry a defined shape due to the gap between its molecules.'

As per the details provided, the inference that can be deduced would be:

"Liquid A is a homogeneous mixture and Liquid B is a heterogeneous mixture."

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Wilhelm Roentgen discovered that a cathode-ray beam striking a glass surface produced a new type of radiation that he named X-rays.

Roentgen was experimenting with cathode rays in a vacuum tube when he noticed that a fluorescent screen in his lab started to glow even though it was not in the direct path of the cathode rays. He determined that a new type of radiation was being emitted from the tube, which he later discovered had the ability to pass through solid objects like human tissue.

Roentgen's discovery of X-rays revolutionized the field of medicine and led to the development of medical imaging techniques like X-ray machines, CT scans, and MRI scans.

The discovery of X-rays had far-reaching implications beyond just medicine. It laid the foundation for a new field of science known as radiology and enabled scientists to study the internal structures of objects without destroying them. X-rays also helped in the development of radiotherapy and cancer treatment by providing a non-invasive method for locating tumors within the body. Today, X-rays are still widely used in the medical field and other industries for various purposes.

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Answer: 3

Explanation:

You want to use the Rydberg equation which is given by

\(E = -R_{H}(\frac{1}{n_{final}^2} - \frac{1}{n_{initial}^2})\)

where \(R_H = 2.18 \, \cdot 10^{-18} J\).

We are however given the wavelength instead of energy, and so we need to represent E in terms of its wavelength, and so we use  \(E = \frac{hc}{\lambda}\). Remember that λ must be in meters in this formula. So we can divide 1284 nm by \(10^9\) to get the wavelength in meters. This gives \(\lambda = 1.284 \, \cdot 10^{-6}\) meters. Putting this all together we have

\(\frac{hc}{\lambda} = -R_{H}(\frac{1}{n_{final}^2} - \frac{1}{n_{initial}^2})\)

where

\(h = 6.626 \cdot 10^{-34} J\cdot s\\c = 2.998 \cdot 10^{8}\, m/s\\\lambda = 1.284 \cdot 10^{-6}\, m\\R_H = 2.18 \, \cdot 10^{-18} J\\n_{initial} = 5\\n_{final} = \, ?\)

If we plug in everything we should get roughly \(n_f = 3.00194\) but remember that orbitals must be a whole number and so you would round to the closest integer which gives \(n_f = 3.\)

The molecule that is NOT part of the thin filament is titin.

The other molecules listed, actin, troponin, and tropomyosin, are all part of the thin filament.

Myofilaments mostly come in two varieties. The two types of filaments are thin filaments and thick filaments.

The thin filaments have a diameter of 7-9 nm. They are joined to the striated muscle's z discs.

Actin, troponin, and tropomyosin are the three proteins that make up each thin filament.

However, the primary protein in the thin filament is actin.

The helical strands of the thin filament, now known as F actin (being fibrous), are made up of 300–400 globular actin molecules that are joined end to end. During the contraction phase, a myosin cross-bridge or head can bind to each actin molecule. Troponin is an additional protein found in the thin filament.

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Un elemento químico, o un elemento, se define como un material que no puede descomponerse ni transformarse en otra sustancia por medios químicos. Cada elemento se identifica según la cantidad de protones que tiene en su núcleo atómico. Se puede crear un nuevo elemento agregando más protones a un átomo.

_________

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ITZY :)

The enthalpy change of PCl₅(g) → PCl₃(g) + Cl₂(g) is

The enthalpy change of 2CO₂(g) + H₂O(g) → C₂H₂(g) + 5/2O₂(g) is

Using Hess' Law, the enthalpy change of the target reaction can be calculated by subtracting the sum of the enthalpy changes of the step reactions from each other. Therefore, the enthalpy change for the given reaction can be calculated as follows:

ΔH = [4PCl₃(g) + 10Cl₂(g)] - [4PCl₅(g)] = -2439 kJ + 3438 kJ = 999 kJ

Using Hess' Law, the enthalpy change of the target reaction can be calculated by subtracting the sum of the enthalpy changes of the step reactions from each other. Therefore, the enthalpy change for the given reaction can be calculated as follows:

ΔH = [C₂H₂(g) + 5/2O₂(g)] - [2H₂(g) + CO₂(g)] = -94.5 kJ + 5/2(-141.0 kJ) - 71.2 kJ = -312.7 kJ

The enthalpy change for the target reaction is calculated by using Hess' Law, which states that the enthalpy change for a reaction is independent of the path taken, and is only dependent on the initial and final states of the system. In the first example, the enthalpy change for the decomposition of PCl₅ is calculated by subtracting the enthalpy change for the formation of PCl₃ and Cl₂ from the enthalpy change for the formation of PCl₅.

The enthalpy change for the combustion of C₂H₂ is calculated by subtracting the enthalpy change for the formation of H₂ and CO₂ from the enthalpy change for the formation of C₂H₂ and O₂.

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A. Larger Crystals Indicate the melt cooled gradually

To solve this problem, let's use the definition for molarity:

Replacing the values of the problem:

Now, to find the mass, we multiply by the molecular weight of NaCl. (Which is about 58.44g/mol)

The answer is approximately 22.2g of NaCl

In the hydrogenation of alcohol, Ethanol is the reducing agent and it loses electron.

Alcohol hydrogenase transform ethanol to Acetaldehyde. This known as carcinogen. In this Acetaldehyde is more toxic compound. Alcohol dehydrogenases catalyze the oxidation of primary and secondary alcohols to the corresponding aldehyde or ketone by the transfer of a hydride anion to NAD+ with release of a proton.

Ethanol + NAD^+ ---> acetaldehyde + NADH + H^+

The half reactions are:

Ethanol --------->Acetaldehyde + 2H^+ + 2e (oxidation)

NAD+ + 2H+ + 2e- ------->NADH + H^+ (Reduction)

Ethanol is oxidized to acetaldehyde, because it loses e- .NAD+ is reduced to NADH, because it gain of e− . NAD is the oxidizing agent. Oxidizing agent gains e− and therefore reduced during reaction. Ethanol is the reducing agent. Reducing agent loses e−and therefore oxidized during reaction . Alcohol dehydrogenase is also involved in the toxicity of other types of alcohol.

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Answer:

its 17.0g NH3

Explanation:

find the number of moles of nitrogen.

Answer:

yes

Explanation:

Answer:

Alpha is the most harmful, Gamma is the least harmful.

Explanation:

From skimming over your answer I have noticed this mistake. You are correct in saying alpha is the least penetrating but incorrect in saying alpha is the least ionising. Same for Gamma.

The compound is hydrogen peroxide as shown.

A molecular model is a representation of a molecule that is used to better understand its properties, behavior, and interactions. Molecular models can be physical, such as models made from plastic or metal, or they can be virtual, such as computer-generated models.

The purpose of a molecular model is to provide a visual and often interactive representation of a molecule's structure, which can aid in the understanding of its chemical and physical properties, as well as its behavior in different environments or under different conditions.

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The pH of the solution resulting from the reaction between barium hydroxide and hydrochloric acid is approximately 1.50.

To calculate the pH of the solution resulting from the reaction between barium hydroxide (Ba(OH)₂) and hydrochloric acid (HCl), we need to determine the concentration of the resulting ions and their contribution to the solution's pH.

Given:

Volume of barium hydroxide (Ba(OH)₂) solution = 38.6 ml

Concentration of barium hydroxide (Ba(OH)₂) solution = 0.100 M

Volume of hydrochloric acid (HCl) solution = 207.1 ml

Concentration of hydrochloric acid (HCl) solution = 0.200 M

The reaction between barium hydroxide and hydrochloric acid can be represented as follows:

Ba(OH)₂ + 2HCl → BaCl₂ + 2H₂O

From the balanced equation, we can see that the reaction results in the formation of barium chloride (BaCl₂) and water (H₂O). Since the reaction goes to completion, all of the barium hydroxide will react with the hydrochloric acid.

First, we can calculate the moles of barium hydroxide and hydrochloric acid used in the reaction:

Moles of Ba(OH)₂ = volume (in liters) × concentration = 0.0386 L × 0.100 M = 0.00386 mol

Moles of HCl = volume (in liters) × concentration = 0.2071 L × 0.200 M = 0.04142 mol

Since barium hydroxide and hydrochloric acid react in a 1:2 ratio, we can determine that 0.00386 mol of barium hydroxide reacts with twice that amount of hydrochloric acid, resulting in 0.00772 mol of hydrochloric acid being consumed in the reaction.

Now, we need to calculate the concentration of hydrochloric acid ions (H⁺) in the resulting solution. The volume of the resulting solution will be the sum of the volumes of barium hydroxide and hydrochloric acid:

Volume of resulting solution = volume of Ba(OH)₂ + volume of HCl = 38.6 ml + 207.1 ml = 245.7 ml = 0.2457 L

To calculate the concentration of H⁺ ions in the resulting solution:

Concentration of H⁺ = moles of H⁺ / volume of resulting solution = 0.00772 mol / 0.2457 L ≈ 0.0314 M

Finally, we can calculate the pH of the solution using the equation:

pH = -log[H⁺] = -log(0.0314) ≈ 1.50

Therefore, The pH of the solution resulting from the reaction between barium hydroxide and hydrochloric acid is approximately 1.50.

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