What is the mass number of an atom which contains 21 electrons, 21 protons, and 24 neutrons?

Explanation:

Density is defined as the degree of compactness or mass per unit volume.

Mathematically,         density = [tex]\frac{mass}{volume}[/tex]

It can be seen from the formula that mass is proportional to density. That is, more is the mass of an object more will be its density.

Therefore, it is given that iron nail sinks to the bottom this means that the iron nail has highest density as compared to the piece of wood and a styrofoam cup.

Thus, we can conclude that given experiment demonstrates the density of given objects.

The Aufbau Principle explains that electrons fill the lowest available energy levels in atomic orbitals before moving to higher levels. It helps determine the electron configuration of atoms, considering the periodic table, Hund's Rule, and the Pauli Exclusion Principle. This principle is essential for understanding atomic structure in chemistry.

The Aufbau Principle (German for “building up” principle) is a fundamental guideline in chemistry used to determine the electron configuration of an atom. It states that electrons fill atomic orbitals of the lowest available energy levels before occupying higher energy levels. In other words, the 1s subshell is filled before the 2s subshell, and the 2s subshell is filled before the 2p subshell, and so on.

This principle helps in constructing the electron configuration of an element by building it up step-by-step through the periodic table. For example, a carbon (atomic number 6) atom has an electron configuration of 1s2 2s2 2p2, which means it has filled the 1s subshell, then the 2s subshell, and finally partially filled the 2p subshell with two electrons.

Additionally, other rules like Hund's Rule and the Pauli Exclusion Principle work alongside the Aufbau Principle to determine the unique arrangement of electrons within orbitals. Hund's Rule states that electrons must occupy every orbital singly before any orbital is doubly occupied, and the Pauli Exclusion Principle asserts that no two electrons can have the same set of quantum numbers.

Utilizing these principles, students can accurately determine the ground-state electron configurations of atoms across the periodic table.

Answer:

it B the answer

Explanation:

hoped you enjoyed the joke :)

Final answer:

Joseph John Thomson discovered the electron, a fundamental negatively charged particle, developing the plum pudding model of the atom and earning a Nobel Prize for his contributions to physics.

Explanation:

British physicist Joseph John Thomson was the first to identify the electron, a negatively charged particle. In 1897, Thomson conducted groundbreaking experiments with cathode rays, proving that they were composed of particles rather than waves, because of their negative electric charge. He achieved this through meticulous experiments sending a pure beam of these particles through crossed electric and magnetic fields and balancing the fields until there was no net deflection of the beam. This allowed him to calculate the charge-to-mass ratio of the electron, revealing that its mass was significantly smaller than any known atom - precisely 1837 times smaller. Thomson's work led to the development of the plum pudding model of the atom, in which the atom was imagined as a sphere of positive charge with electrons dispersed within it, similar to plums in a pudding. His pioneering work paved the way for our modern understanding of the atomic structure and for this, he was awarded the Nobel Prize in Physics in 1906.

Answer:

[tex]2.0 g/cm^3 [/tex]is the density of the solid .

Explanation:

Mass of the solid = m = 3.60 g

Volume of the solid = V = [tex]1.8 cm^3[/tex]

Density of the solid ,d = ?

[tex]Density=\frac{Mass}{Volume}[/tex]

[tex]d=\frac{m}{V}=\frac{3.60 g}{1.8 cm^3}=2.0 g/cm^3 [/tex]

[tex]2.0 g/cm^3 [/tex]is the density of the solid .

Answer:

An easy way to remember the diatomic molecules is HOFBrINCl

almost sounds like hofbrinkle

Final answer:

The name for SO2 is sulfur dioxide, where 'sulfur' is the name of the element and 'dioxide' indicates the presence of two oxygen atoms.

Explanation:

The name for SO2 is sulfur dioxide. This compound is a mixture of sulfur and oxygen, where the sulfur atom is joined by two oxygen atoms. Sulfur, being lower in the periodic table, comes first in the compound's name. Since there are two oxygen atoms, we use the prefix 'di-' to indicate the quantity, resulting in 'dioxide' when combined with the stem 'ox-' and the suffix '-ide'. Therefore, the complete chemical name is sulfur dioxide. It is important to note that sulfur forms another common compound with oxygen, which is SO3 or sulfur trioxide. Each of these compounds has distinct chemical and physical properties, necessitating unique names for accurate identification.

ANSWER

Lithium, rhenium , mercury , are metals out of given five elements.

As lithium is a alkali metal , rhenium and mercury both are transition metals.

based on the electronic configurations of the metals , they have valence electrons present in their valence shell  which are easily available for donation so that they can attain stable electronic configuration and thus they are considered as metals.

boron is a non metal which is the member of group 13 of the periodic table.

krypton is a noble gas which is a member of group 18 of the periodic table.

phosphorus is a non metal member of group 17 of the periodic table.

To balance chemical equations, coefficients are adjusted so that the number of each type of atom and the charge are the same on both sides. For example, the reaction between magnesium and oxygen is balanced by writing 2Mg + O2 → 2MgO, demonstrating the principle of conservation of mass.

Balancing chemical equations involves adding coefficients to the reactants and products so that the same number of each type of atom occurs on both sides of the equation. To balance the listed equations:

The key to balancing equations is to systematically adjust coefficients, ensuring both mass and charge are conserved.

I just answered on my test. the answer is B.

The statement, that describes which must be true of Solution 2 that poured into Solution 1 with pH of 6.5 is "It is more acidic than Solution 1."

A solution's pH is a measure of its hydrogen ion concentration, which is a measure of its acidity. In other terms, pH is a scale that specifies the acidity or basicity of an aqueous solution.

The scale ranges from zero (the most acidic) to fourteen (the most basic). The pH scale above shows that pure water has a pH value of 7. That is, pH values less than 7 are acidic, while pH values greater than 7 are alkaline (basic). As a result, solution 2 is acidic and contains more hydrogen ions than solution 1, because an acidic solution has a pH value less than 7.

Hence the correct answer is more acidic than Solution 1.

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Final answer:

The balanced chemical equation for the standard heat of formation of CrO3(s) at 298 K is 2Cr(s) + 3/2O2(g) → Cr2O3(s). The standard heat of formation of CrO3(s) can be calculated using the standard heats of formation of the elements Cr(s) and O2(g) and the standard heat of formation of Cr2O3(s).

Explanation:

The balanced chemical equation for the standard heat of formation of CrO3(s) at 298 K is:

2Cr(s) + 3O2(g) + 3/2O2(g) → Cr2O3(s)

Now, we need to apply the equation to calculate the standard heat of reaction from the standard heats of formation. The standard heat of formation of a compound is the enthalpy change when one mole of the compound is formed from its constituent elements in their standard states. The standard heat of formation of CrO3(s) can be determined by subtracting the standard heat of formation of the reactants from the standard heat of formation of the product.

Therefore, the balanced chemical equation for the standard heat of formation of CrO3(s) at 298 K is 2Cr(s) + 3/2O2(g) → Cr2O3(s), and the standard heat of formation of CrO3(s) can be calculated using the standard heats of formation of the elements Cr(s) and O2(g) and the standard heat of formation of Cr2O3(s).

Since so much of the data is shared and evaluated around the world, using the same measurement systems allows for no confusion among scientists. When they discuss and report, everyone understands what is being communicated.

No because he did have a small idea allowing later more educated scientist in more modern times to review and find mistakes. This allowed scientist in more modern times to also have develop theories. Every idea needs fixing and this is one. Since he was first to know about such atoms and making the "plum pudding model", he gave scientists some thoughts or possible ideas as to what a substance would be like after its last piece.

The molar heat of combustion of methanol is -745kJ/mol

This is heat released to the environment when one mole of a substance in this case methanol is completely burned.

Data given;

The number of moles of methanol is the ratio between the mass to the molar mass of methanol

[tex]n=\frac{m}{M}\\n=\frac{1.922}{32}\\n=0.06moles[/tex]

The number of moles present in 1.922g of methanol is 0.06moles.

This is the heat required to completely burn a substance

[tex]Q=mc[/tex]ΔT

[tex]Q=8.69*5.14=44.67kJ[/tex]

ΔH = [tex]-(\frac{Q}{n})[/tex]

n = number of moles

ΔH = [tex]-\frac{44.7}{0.06}=-745kJ/mol[/tex]

The molar heat of combustion is -745kJ/mol

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The answer is No, it is not possible that the reverse reaction will occur at ordinary conditions. This is because the entropy of the KCl and the O2 are much largely negative than that of the KClO3. The entropy component of the Gibbs free energy assures that the Gibbs free energy for the reverse reaction is positive (Positive Gibbs means nonspontaneous reaction). 

The formation of [tex]\( \text{KClO}_3 \)[/tex] from [tex]\( \text{KCl} \)[/tex] and [tex]\( \text{O}_2 \)[/tex] is not likely feasible under ordinary conditions due to its endothermic nature and decrease in entropy.

The decomposition of [tex]\( \text{KClO}_3 \)[/tex] into [tex]\( \text{KCl} \)[/tex] and [tex]\( \text{O}_2 \)[/tex] is exothermic and increases entropy, making it spontaneous under ordinary conditions. The reverse reaction, forming [tex]\( \text{KClO}_3 \)[/tex] from [tex]\( \text{KCl} \)[/tex] and [tex]\( \text{O}_2 \)[/tex], would be endothermic and decrease entropy, requiring energy input and typically not occurring spontaneously under normal conditions. Therefore, the formation of  [tex]\( \text{KClO}_3 \)[/tex] from [tex]\( \text{KCl} \)[/tex] and [tex]\( \text{O}_2 \)[/tex] is not likely to be feasible under ordinary conditions.

" Two physical properties are melting point and boiling point. Two chemical properties are reactivity with other substances and flammability.

 Explanation:

 Physical properties are characteristics that can be observed without changing the identity or composition of the substance. They are used to describe matter and can be measured or perceived with the senses. Two examples of physical properties are:

  1. Melting point: This is the temperature at which a solid substance transitions to a liquid. It is a physical property because it does not involve a chemical change; the substance remains the same before and after melting.

 2. Boiling point: This is the temperature at which a liquid substance changes to a gas at a given pressure. Similar to melting point, boiling point is a physical property as it describes a physical change of state without altering the chemical composition of the substance.

  Chemical properties, on the other hand, describe the ability of a substance to undergo a chemical change or reaction. They are concerned with the chemical structure and composition of the substance. Two examples of chemical properties are:

  1. Reactivity with other substances: This refers to the tendency of a substance to react with other chemicals. For instance, some metals react with acids to produce hydrogen gas. This property is a chemical property because it involves a change in the chemical identity of the substances involved.

 2. Flammability: This is the ability of a substance to burn in the presence of oxygen. When a material burns, it undergoes a chemical reaction, often combining with oxygen to form new compounds such as carbon dioxide and water. Flammability is therefore a chemical property as it involves a chemical transformation."

Deviations from the idealized bond angle occur due to the presence of lone electron pairs on the central atom. For the molecules PF3 and SBr2, the bond angles deviate from the ideal angles because of the lone pairs on the central atoms. On the contrary, CS2 and CHCl3, with no lone pairs on the central atom, do not deviate.

In Chemistry, deviations from the idealized bond angle are typically observed in molecules where one or more of the central atoms possess lone electron pairs. These lone pairs keep more space causing the bond angles to be less than the ideal angles predicted by the VSEPR (Valence Shell Electron Pair Repulsion) model.

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Answer:

Corn

Explanation:

Being a plant and having chlorophyll in its structures, corn is able to capture sunlight and converting it into chemical energy, through photosynthesis.

Photosynthesis is a process carried out by plants to produce their own food. The plant draws carbon dioxide from the air and energy from the sun. Through this process, the plant produces its own food consisting essentially of glucose.

Briefly, we can say that photosynthesis uses carbon dioxide, water and sunlight (in the form of heat) to produce organic compounds (glucose) and oxygen.

A solar cell is the object that converts light to chemical energy.

The correct answer to the given question is option d.

The object that converts light to chemical energy is option d. solar cell.

A solar cell absorbs photons with energy greater than its energy gap and converts them into electrical energy using the photoelectric effect.

For example, a solar panel harnesses the power of sunlight and converts it into electricity.

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Final answer:

Herodotus, in his work 'The Histories', explored the cultural differences between Greeks, Persians, and Egyptians, documenting complex societies and challenging the notion of cultural superiority.

Explanation:

Herodotus is known as the father of history, and in his work, The Histories, he delves into the cultural contrasts between Greeks, Persians, and Egyptians. He observed that, despite the Greek perspective that often labeled Persians as "barbarians," other societies such as Persia could rival Greece in complexity and military prowess. In Egypt, he noted differences in religious practices and governance, recognizing the peaceable hereditary transfer of power in contrast to the often tumultuous Greek city-state politics.

Herodotus was well-traveled and utilized his experiences to explore the encounter between different cultures. His inquiry aimed to ensure that "great and marvelous deeds" by both Greeks and non-Greeks would not be forgotten. This exploration led him to challenge the notion of one culture being superior to another and opened a dialogue about cultural relativism that remains relevant.

Eukaryotic cells have specialized structures called organelles suspended in the cytoplasm, each with their own unique functions.

Eukaryotic cells have specialized structures suspended in the cytoplasm, known as organelles, which carry out specific functions.

Some of the organelles found in eukaryotic cells include:

These organelles, among others, contribute to the overall function and organization of eukaryotic cells.

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