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2 years ago

Please help , I don't know about big bang I'm sorry

Chemistry

1 answer:

Tresset [83]2 years ago

3 0

1. When our Galaxy was forming why was the center dense?

Answer: Stars are believed to originate as from gas clouds in space. Gravitational forces cause this gas to contract forming a dense center of gravitational force.Eventually this extreme pressure at the center of the star causes nuclear fusion reactions to occur.

2. Why did hydrogen atoms collide in the dense center of the Galaxy?

Answer: Compression would heat the gas to temperatures above 1,000 kelvins. Some hydrogen atoms would pair up in the dense, hot gas, creating trace amounts of molecular hydrogen. The hydrogen molecules would then start to cool the densest parts of the gas by emitting infrared radiation after they collide with hydrogen atoms.

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A gas is collected at 20.0 °C and 725.0 mm Hg. When the temperature is

krek1111 [17]

Answer:

676mmHg

Explanation:

Using the formula;

P1/T1 = P2/T2

Where;

P1 = initial pressure (mmHg)

P2 = final pressure (mmHg)

T1 = initial temperature (K)

T2 = final temperature (K)

According to the information provided in this question;

P1 = 725.0mmHg

P2 = ?

T1 = 20°C = 20 + 273 = 293K

T2 = 0°C = 0 + 273 = 273K

Using P1/T1 = P2/T2

725/293 = P2/273

Cross multiply

725 × 273 = 293 × P2

197925 = 293P2

P2 = 197925 ÷ 293

P2 = 676mmHg.

The resulting pressure is 676mmHg

3 0

3 years ago

Rank the following elements by effective nuclear charge, Zeff, for a valence electron. F LI Be B N

Stels [109]

Answer:

Rank in increasing order of effective nuclear charge:

Li < Be < B < N < F

Explanation:

This explains the meaning of effective nuclear charge, Zeff, how to determine it, and the calculations for a valence electron of each of the five given elements: F, Li, Be, B, and N.

1) Effective nuclear charge definitions

While the total positive charge of the atom nucleus (Z) is equal to the number of protons, the electrons farther away from the nucleus experience an effective nuclear charge (Zeff) less than the total nuclear charge, due to the fact that electrons in between the nucleus and the outer electrons partially cancel the atraction from the nucleus.

Such effect on on a valence electron is estimated as the atomic number less the number of electrons closer to the nucleus than the electron whose effective nuclear charge is being determined: Zeff = Z - S.

2) Z eff for a F valence electron:

F's atomic number: Z = 9
Total number of electrons: 9 (same numer of protons)
Period: 17 (search in the periodic table or do the electron configuration)
Number of valence electrons: 7 (equal to the last digit of the period's number)
Number of electrons closer to the nucleus than a valence electron: S = 9 - 7 = 2
Zeff = Z - S = 9 - 2 = 7

3) Z eff for a Li valence eletron:

Li's atomic number: Z = 3
Total number of electrons: 3 (same number of protons)
Period: 1 (search on the periodic table or do the electron configuration)
Number of valence electrons: 1 (equal to the last digit of the period's number)
Number of electrons closer to the nucleus than a valence electron: S = 3 - 1 = 2
Z eff = Z - S = 3 - 2 = 1.

4) Z eff for a Be valence eletron:

Be's atomic number: Z = 4
Total number of electrons: 4 (same number of protons)
Period: 2 (search on the periodic table or do the electron configuration)
Number of valence electrons: 2 (equal to the last digit of the period's number)
Number of electrons closer to the nucleus than a valence electron: S = 4 - 2 = 2
Z eff = Z - S = 4 - 2 = 2

5) Z eff for a B valence eletron:

B's atomic number: Z = 5
Total number of electrons: 5 (same number of protons)
Period: 13 (search on the periodic table or do the electron configuration)
Number of valence electrons: 3 (equal to the last digit of the period's number)
Number of electrons closer to the nucleus than a valence electron: S = 5 - 3 = 2
Z eff = Z - S = 5 - 2 = 3

6) Z eff for a N valence eletron:

N's atomic number: Z = 7
Total number of electrons: 7 (same number of protons)
Period: 15 (search on the periodic table or do the electron configuration)
Number of valence electrons: 5 (equal to the last digit of the period's number)
Number of electrons closer to the nucleus than a valence electron: S = 7 - 5 = 2
Z eff = Z - S = 7 - 2 = 5

7) Summary (order):

Atom Zeff for a valence electron

Li 1

Be 2

Conclusion: the order is Li < Be < B < N < F

6 0

3 years ago

Please help with 3 and 4

mafiozo [28]

3. volume of gas because its changing because of the temperature
4. 67.6 breaths per minute
65+73+67+71+62=338/5=67.6
^because there are five terms that we added

7 0

2 years ago

True or False. Isotopes have different chemical properties. Explain why?

Maurinko [17]

Answer:

False

Explanation: isotopes generally have the same physical and chemical properties because they have the same numbers of protons and electrons.

4 0

2 years ago

The energies of electrons are quantized. What does that mean?.

professor190 [17]

Answer:

The correct statement should be The energies of electron are quantized when they are bounded to an atom.

In Quantum Mechanics The term Quantization used to measure the physical entities having certain discrete value. When we say energies of electron are quantized that means it have some specific values that are allowed, that is not continuous range of values.

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4 0

1 year ago