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3 years ago

Which of the following elements contains 7 valence electrons?

Chemistry

2 answers:

Evgesh-ka [11]3 years ago

7 0

Answer:

Halogens

Explanation:

Because elements can have 8 valence elctrons so noble gas group 18 has 8 valence electrons and previous group before group 18 or noble gas is called Halogens or group 17 whatever you want to prefer periodic table has all of informations

Liono4ka [1.6K]3 years ago

6 0

Answer:

Elements: F, Cl, Br, I, At

Explanation:

Hi there,

When you are trying to find the valence electrons for an element, look at the last number of the electron configuration.

For example, if you want to find the number of valence electrons of Carbon (C), you notice that the electron configuration is<u> 2 - 4.</u>

We know that this element has four valence electrons because the last number in its electron configuration is 4.

For your question, simply find all of the elements that have the number 7 as the last number on its electron configuration on the periodic table.

Hope this answer was helpful. Cheers.

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3 years ago

Read 2 more answers

What does the chemical formula CaCl, show about the compound it represents? It is made up of one element. It is made up of two e

zavuch27 [327]

Answer:

It is made up of two elements.

Explanation:

To answer the question given above,

We shall determine the number of elements present in CaCl₂. This can be obtained as follow:

CaCl₂ contains calcium (Ca) and chlorine gas (Cl₂).

This implies that CaCl₂ contains two different elements.

Now, considering the options given in the question above, CaCl₂ is made up of two elements.

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3 years ago

Calculate the molar concentration of the Br⁻ ions in 0.065 M MgBr2(aq).

steposvetlana [31]

MgBr2(aq) is an ionic compound which will have the releasing of 2 Br⁻ ions ions in water for every molecule of MgBr2 that dissolves.
MgBr2(s) --> Mg+(aq) + 2 Br⁻(aq)
[Br⁻] = 0.065 mol MgBr2/1L × 2 mol Br⁻ / 1 mol MgBr2 = 0.13 M
The answer to this question is [Br⁻] = 0.13 M

4 0

3 years ago

What is the pH of a solution in which [H 3O +] = 3.8 × 10 -8 M?

7nadin3 [17]

Answer:

<h3>The answer is 7.42 </h3>

Explanation:

The pH of a solution can be found by using the formula

$pH = - log [ { H_3O}^{+}]$

From the question we have

$pH = - log(3.8 \times {10}^{ - 8} ) \\ = 7.420216...$

We have the final answer as

Hope this helps you

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3 years ago

The value of Ka for nitrous acid (HNO2) at 25 ∘C is 4.5×10−4 .a. Write the chemical equation for the equilibrium that correspond

kvv77 [185]

Answers and Explanation:

a)- The chemical equation for the corresponden equilibrium of Ka1 is:

2. HNO2(aq)⇌H+(aq)+NO−2

Because Ka1 correspond to a dissociation equilibrium. Nitrous acid (HNO₂) losses a proton (H⁺) and gives the monovalent anion NO₂⁻.

b)- The relation between Ka and the free energy change (ΔG) is given by the following equation:

ΔG= ΔGº + RT ln Q

Where T is the temperature (T= 25ºc= 298 K) and R is the gases constant (8.314 J/K.mol)

At the equilibrium: ΔG=0 and Q= Ka. So, we can calculate ΔGº by introducing the value of Ka:

⇒ 0 = ΔGº + RT ln Ka

ΔGº= - RT ln Ka

ΔGº= -8.314 J/K.mol x 298 K x ln (4.5 10⁻⁴)

ΔGº= 19092.8 J/mol

c)- According to the previous demonstation, at equilibrium ΔG= 0.

d)- In a non-equilibrium condition, we have Q which is calculated with the concentrations of products and reactions in a non equilibrium state:

ΔG= ΔGº + RT ln Q

Q= ((H⁺) (NO₂⁻))/(HNO₂)

Q= ( (5.9 10⁻² M) x (6.7 10⁻⁴ M) ) / (0.21 M)

Q= 1.88 10⁻⁴

We know that ΔGº= 19092.8 J/mol, so:

ΔG= ΔGº + RT ln Q

ΔG= 19092.8 J/mol + (8.314 J/K.mol x 298 K x ln (1.88 10⁻⁴)

ΔG= -2162.4 J/mol

Notice that ΔG<0, so the process is spontaneous in that direction.

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4 years ago