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Answer:

1. The temperature increases in the center of a nebula, and nuclei begin to fuse.

2. As the nuclear fusion sets off a chain reaction, the nebula gets hotter and brighter and turns into a star.

3. The star stays in the main sequence stage for a long time.

4. The star runs out of hydrogen and turns into a planetary nebula or a supernova, depending on its mass.

5. Heavy elements are created when the supernova explodes.

6. All that remains of the star now is the core. In some cases, the star turns into a black hole.

Explanation:

The atomic mass of lead : 207 g/mol

The mass of this basic particle is expressed in atomic mass units  

This atomic unit uses the standard atomic mass, that is, the C-12 isotope

1 atom C-12 = 12 atomic mass units

The atomic mass of an element (amu = u = g/mol) = the mass in grams of one mole of an element.

The mass of 0.2 mol of Lead equals 41.4 grams​, so the atomic mass :

[tex]\tt \dfrac{41.4}{0.2}=207~g/mol[/tex]

Answer:

the answer is A

Explanation:

i took the test on edg.                  sorry it is so late:(

Answer:A

Explanation:

Answer:

You're answer is B.

Explanation:

Covalent Bonds share a negative and positive ion.

In covalent bonding, electrons are shared because sharing allows them to achieve a noble gas configuration. Therefore, option (A) is correct.

A covalent bond is created by the equal sharing of electrons from both bonded atoms. The pair of electrons contributing to this type of bonding is known as shared pair.

Covalent bonds are also known as molecular bonds. Sharing of bonding pairs will make sure that the atoms attain stability in their outer shell as the atoms of noble gases.

Elements with very high ionization energies are not capable of transferring electrons and elements with very low electron affinity cannot accept electrons. Such atoms tend to share their electrons with the other atoms of the same element in a way that both atoms can achieve octet configuration in their valence shell.

This type of association through sharing of electrons between different or the same kinds is called Covalent Bond. Covalent bonds rarely dissociate spontaneously after formation.

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Answer:

c. kinetic energy

Explanation:

Answer:

A physical change is any change in matter that involves the substance going from one physical state to another. The reference to a physical state involves solids, liquids, and gases.

Explanation:

Answer:

i think A.

Explanation:

Answer:

The versions of an element with different neutrons have different masses and are called isotopes. The average atomic mass for an element is calculated by summing the masses of the element's isotopes, each multiplied by its natural abundance on Earth.

Explanation:

Answer: Nuclear fusion is a nuclear reaction where atomic nuclei of a low atomic number fuse to form a heavier nucleus releasing energy.

Explanation:

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Actually Welcome to the Concept of the Chemical bonds.

Due to the presence of dipole-dipole forces, polar covalent molecules like water tend to be _____ at room temperature.

The answer is Liquids

Water tends to be liquids at the room temperature.

Explanation:

3)

Equation -

3F₂ (g) + 2AlBr₃ (s) → 3Br₂ (l) + 2AlF₃ ↓

4)

When sulphur dioxide gas reacts with oxygen then it forms sulphur trioxide gas.

Equation -

2SO₂ (g) + O₂ (g) → 2SO₃ (g)

Answer:

The answer will be listed below.

Explanation:

An acid is a substance that produces (H+) as the only positive ion when mixed with water. A base is a substance that produces (OH–) as the only negative ion when mixed with water.

Answer:

An acid increases the concentration, A base is a substance that releases hydroxide

Explanation: A base donates electrons and accepts protons, and acid is a substance that donates protons.

Answer:

B

Explanation:

electron.elements of the same group have the same electrons

Answer:

Inferred that fossils were once part of living animals.

Explanation:

He realized that seashells that were from rocks were identical to ones on a beach.

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Hello there!

Your answer is C.

Answer:

The right option is; A. It is younger than the rock layer below.

Explanation:

A rock layer deposited on top of another rock layer is younger than the rock layer below. This is based on the law of superposition which states that in any undeformed sequence of rocks that are laid down in layers, the youngest layer of rock will be on top of the sequence, while the oldest layer will be at the bottom of the sequence.

Answer:

For #3 I believe it's A

Explanation:

It can't be changed INTO a solid because it already is one.

Hope this helps!

Answer:

P2 = 1.2265 atm (Approx)

Explanation:

Given:

Water temperature = 25 degree Celsius

Pressure = 1 atm

So,

P1/P2 = C1/C2

1 / P2 = 0.061 / 0.075

P2 = 1.2265 atm (Approx)

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Actually Welcome to the Concept of the Ionic bonds.

Since Sodium (Na) is a cation and Chlorine (Cl) is a Anion, they both form a Ionic bond called as NaCl (common salt)

So answer is, Na and Cl

Answer:

A. Kinetic Energy

Explanation:

Thermal energy is when the molecules and atoms are vibrating faster due to higher temperatures.

Kinetic energy fits this because the meaning of it is the energy of a moving object.

Since thermal energy comes from moving molecules and atoms, it is therefore a for of kinetic energy.

Answer:

Oxygen production.

Explanation:

Answer: D 25 degrees

Explanation: The reason because is 25x4=100 and slightly tilted =1/4 of the earth which is 25

Answer:

have the same number of atoms

Explanation:

Atoms of the same element have the same atomic number so the number of protons (and electrons) are same. But they have same or different mass number (like that for isotopes) . Different mass number will have different number of neutrons.

Answer:

Same number of atoms

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Explanation:

Answer:

270

Explanation:

Once you add more mass to something the mass doesn’t go away you add more mass.

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Answer:

Mass can neither be created nor destroyed in a chemical equation, it  transfer from one to another form.

Explanation:

Law of conservation of mass:

According to the law of conservation mass, mass can neither be created nor destroyed in a chemical equation.

Explanation:

This law was given by French chemist  Antoine Lavoisier in 1789. According to this law mass of reactant and mass of product must be equal, because masses are not created or destroyed in a chemical reaction.

For example:

In given photosynthesis reaction:

6CO₂ + 6H₂O + energy → C₆H₁₂O₆ + 6O₂

there are six carbon atoms, eighteen oxygen atoms and twelve hydrogen atoms on the both side of equation so this reaction followed the law of conservation of mass.

Changes in shape and state are the two characteristics  which indicate a physical change.

Physical changes are defined as changes which affect only the form of a substance but not it's chemical composition. They are used to separate mixtures in to chemical components but cannot be used to separate compounds to simpler compounds.

Physical changes are always reversible using physical means and involve a change in the physical properties.Examples of physical changes include melting,boiling , change in texture, size,color,volume and density.Magnetism, crystallization, formation of alloys are all reversible and hence physical changes.

They involve only rearrangement of atoms and are often characterized to be changes which are reversible.

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