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4 years ago

Do valence electrons show a repeating or periodic pattern? Explain.

Chemistry

1 answer:

icang [17]4 years ago

6 0

Answer:

Yes, valence electrons show a repeating or periodic pattern.

Explanation:

It is precisely the repeating pattern of the valence electrons which is the responsible for the repeating pattern of the chemical properties: elements on a same group (column) of the periodic table have similar chemical properties because they have the same number of valence electrons.

The chemical changes (reactions) are the result of the interaction of the electrons of the elements, and, since the valence electrons are the outer most electrons, you can expect that it is the valence electrons which most influence the occurrence of the chemical reactions, which is what defines the chemical properties.

Here you have the pattern of the valence electrons shown by the representative elements on the periodic table:

Group number number of valence electrons

(column number)

1 1

2 2

13 3 (the ones digit of the column number)

14 4 (the ones digit of the column number)

15 5 (the ones digit of the column number)

16 6 (the ones digit of the column number)

17 7 (the ones digit of the column number)

18 8 (the ones digit of the column number)

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Based on the molecular structures of chloromethane and methane shown, a student makes the claim that a pure sample of chlorometh

goblinko [34]

Answer:

Yes, chloromethane has stronger intermolecular forces than a pure sample of methane has.

Explanation:

In both methane and chloromethane, there are weak dispersion forces. However, in methane, the dispersion forces are the only intermolecular forces present. Also, the lower molar mass of methane means that it has a lower degree of dispersion forces.

For chloromethane, there is in addition to dispersion forces, dipole-dipole interaction arising from the polar C-Cl bond in the molecule. Also the molar mass of chloromethane is greater than that of methane implying a greater magnitude of dispersion forces in operation.

Therefore, chloromethane has stronger intermolecular forces than a pure sample of methane has.

7 0

3 years ago

If Steve throws a football 57 meters in 3 seconds, what is the average speed of the football?

sattari [20]

Answer:

19 m/s

Explanation:

57/3

7 0

3 years ago

What is the vapor pressure of the solution if 35.0 g of water is dissolved in 100.0 g of ethyl alcohol at 25 ∘C? The vapor press

masya89 [10]

Answer: The vapor pressure of the solution is 43.55 mmHg

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ .....(1)

For water:

Given mass of water = 35.0 g

Molar mass of water = 18 g/mol

Putting values in equation 1, we get:

$\text{Moles of water}=\frac{35.0g}{18g/mol}=1.944mol$

For ethyl alcohol:

Given mass of ethyl alcohol = 100.0 g

Molar mass of ethyl alcohol = 46 g/mol

Putting values in equation 1, we get:

$\text{Moles of ethyl alcohol}=\frac{100.0g}{46g/mol}=2.174mol$

Total moles of solution = [1.944 = 2.174] moles = 4.118 moles

Mole fraction of a substance is given by:

$\chi_A=\frac{n_A}{n_A+n_B}$

For water:

$\chi_{\text{water}}=\frac{n_{\text{water}}}{n_{\text{water}}+n_{\text{ethyl alcohol}}}$

$\chi_{water}=\frac{1.944}{4.118}=0.472$

For ethyl alcohol:

$\chi_{\text{ethyl alcohol}}=\frac{n_{\text{ethyl alcohol}}}{n_{\text{water}}+n_{\text{ethyl alcohol}}}$

$\chi_{\text{ethyl alcohol}}=\frac{2.174}{4.118}=0.528$

Dalton's law of partial pressure states that the total pressure of the system is equal to the sum of partial pressure of each component present in it.

To calculate the vapor pressure of the solution, we use the law given by Dalton, which is:

$P_T=\sum_{i=1}^n (p_i\times \chi_i)$

Or,

$P_T=[(p_{\text{water}}\times \chi_{\text{water}})+(p_{\text{ethyl alcohol}}\times \chi_{\text{ethyl alcohol}}$

We are given:

Vapor pressure of water = 23.8 mmHg

Vapor pressure of ethyl alcohol = 61.2 mmHg

Putting values in above equation, we get:

$p_T=[(23.8\times 0.472)+(61.2\times 0.528)]\\\\p_T=43.55mmHg$

Hence, the vapor pressure of the solution is 43.55 mmHg

4 0

4 years ago

Which response has both answers correct? Will a precipitate form when 250 mL of 0.33 M Na 2CrO 4 are added to 250 mL of 0.12 M A

olchik [2.2K]

Answer:

A precipitate will form.

[Ag⁺] = 2.8x10⁻⁵M

Explanation:

When Ag⁺ and CrO₄²⁻ are in solution, Ag₂CrO₄(s) is produced thus:

Ag₂CrO₄(s) ⇄ 2 Ag⁺(aq) + CrO₄²⁻(aq)

Ksp is defined as:

Ksp = 1.1x10⁻¹² = [Ag⁺]² [CrO₄²⁻]

Where the concentrations [] are in equilibrium

Reaction quotient, Q, is defined as:

Q = [Ag⁺]² [CrO₄²⁻]

Where the concentrations [] are the actual concentrations

If Q < Ksp, no precipitate will form, if Q >= Ksp, a precipitate will form,

The actual concentrations are -Where 500mL is the total volume of the solution-:

[Ag⁺] = [AgNO₃] = 0.12M ₓ (250mL / 500mL) = 0.06M

[CrO₄²⁻] = [Na₂CrO₄] = 0.33M × (250mL / 500mL) = 0.165M

And Q = [0.06M]² [0.165M] = 5.94x10⁻⁴

As Q > Ksp; a precipitate will form

In equilibrium, some Ag⁺ and some CrO₄⁻ reacts decreasing its concentration until the system reaches equilibrium. Equilibrium concentrations will be:

[Ag⁺] = 0.06M - 2X

[CrO₄²⁻] = 0.165M - X

Where X is defined as the reaction coordinate

Replacing in Ksp expression:

1.1x10⁻¹² = [0.06M - 2X]² [0.165M - X]

Solving for X:

X = 0.165M → False solution. Produce negative concentrations.

X = 0.0299986M

Replacing, equilibrium concentrations are:

[Ag⁺] = 0.06M - 2(0.0299986M)

[CrO₄²⁻] = 0.165M - 0.0299986M

[CrO₄²⁻] = 0.135M

6 0

4 years ago

Whats does the elements Li (lithium),B (boron, and Ne neon) have in common?

nikdorinn [45]

They are in the same period (horizontal)

8 0

3 years ago