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2 years ago

How to tell how many valence electrons an atom has?

Chemistry

1 answer:

lbvjy [14]2 years ago

6 0

Answer: Count only the electrons in the highest shell s and p orbitals when determining valence.

Explanation: I'm glad you asked this question. It is often not well explained. The term valence electrons is assigned to only the electrons in an element's highest energy level. These reside only in the s and p orbitals, and not the d or f, as I'll explain later. The s orbital can hold 2 electrons and the p can hold 6. Potassium, K, has an s orbital in its highest energy shell, 4. It contains only 1 electron, so it has a valency of 1.

Calcium, Ca, has 2 in its highest energy level: 4s^2, so it has a valency of 2. Moving to the right, the element scandium, Sc, add another electron, but it goes into the 3d orbital. 3d is in the 3rd energy shell, so it is not counted as a valence electron. Only after we move further right, to gallium, Ga, do we start adding electrons to the 4th energy level again - the 4p orbitals can accept up to 6 electrons. Ga has 3 valence electrons - 2 in the 4s and 1 in the 4p. Oxygen has 2 in the 2s and 4 in the 4p orbitals, for a total of 6. It is close to having a comple outer shell (2 in the 2s and 6 in the 2p). Just 2 more electrons would fill both the 2s and 2p orbitals for a total of 8 valence electrons, a stable configuration (the same configuration as thje stable gas Neon).

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4.50 g of a certain Compound X, known to be made of carbon, hydrogen and perhaps oxygen, and to have a molecular molar mass of 1

Anna11 [10]

Answer:

$\mathbf{C_{10}H_8}$ ( Naphthalene )

Explanation:

Given that:

4.50 g of a Compound X is made up of Carbon , Hydron and Oxygen

It's molecular molar mass = 128 g/mol

Compound X undergoes combustion reaction and the product yield :

CO_2 with mass 15.47g and :

H_2O with mass 2.53 g

The objective is to use this information to determine the molecular formula of X.

We all know that ; number of moles = mass/molar mass

where the molar mass of H_2O is 18 g/mol

number of moles of H_2O product = 2.53 g/18 g/mol

number of moles of H_2O product = 0.1406 moles

Also; the molar mass of CO_2 product = 44 g/mol

number of moles of CO_2 product = 15.47g/ 44 g/mol

number of moles of CO_2 product = 0.3516 moles

number of moles of Compound X in the reactant side= 4.50 g /128 g/mol

number of moles of Compound X n the reactant side= 0.03516 moles

Now; number number of moles of CO_2 in reactant = 0.3516 moles/0.03516 moles

Now; number number of moles of CO_2 in reactant = 10

number of moles of H_2O reactant = 0.1406 moles × 2/0.03516

number of moles of H_2O reactant = 7.997 ≅ 8

Since we said the Compound X is known to be made of Carbon C , Hydrogen H and Oxygen O

Then the molecular formula can be written as :

$\mathbf{C_{10}H_8O_{x}}$

In order to find the x; we have

128 = (12 × 10 + 1 × 8 + 16 × x)

128 = 120 + 8 + 16x)

128 = 128 + 16 x

128 - 128 = 16 x

0 = 16 x

x = 0/16

x = 0

As x = 0 ; hence there are no oxygen present in the reaction

Thus; the molecular formula of Compound X = $\mathbf{C_{10}H_8}$ which is also known as Naphthalene

5 0

3 years ago

Help me<br><br> Extra points

aleksley [76]

G: maintain homeostasis

3 0

3 years ago

Read 2 more answers

Give the n for the following orbitals<br>a. 3p<br>b. 4f

zlopas [31]

Answer:

a. n = 3

b. n = 4

Explanation:

n is just the number in front of the orbital, as n represents the energy level of the orbital.

5 0

3 years ago

Read 2 more answers

Suppose that a person eats a diet of 2391 Calories per day.a.) Convert this energy into J. Express your answer using four signif

alekssr [168]

Explanation:

(a)

The given data is:-

Energy = 2391 Calories

The conversion of calories to J is shown below as:-

1 calorie = 4.184 J

So,

Energy = 4.184 * 2391 J = 10003.944 J

Answer in four significant digits: - $1.000\times 10^4\ J$

(b)

The conversion of calories to kJ is shown below as:-

1 calorie = 0.004184 kJ

So,

Energy = 0.004184 * 2391 kJ = 10.003944 kJ

Answer in four significant digits: - $1.000\times 10\ kJ$

(c)

The conversion of calories to kWh is shown below as:-

1 calorie = $1.1622\times 10^{-6}$ kWh

So,

Energy = $1.1622\times 10^{-6}\times 2391$ kWh = 0.002778873 kWh

Answer in four significant digits: - $0.002779\ kWh$

8 0

3 years ago

A) The change in the internal energy of a system that absorbs 2,500 J of heat and that does 7,655 J of work on the surroundings

Phoenix [80]

Answers:

a) 10155 J

b) 16.6 J

Explanation:

According to the First Law of Thermodynamics we have:

$\Delta E=Q + W$

Where:

$\Delta E$ is the total change in the internal energy of a system

$Q$ is the heat exchanged between the system and its surroundings

$W$ is the work done on the system

a) In this case $Q=2500 J$ and $W=7655 J$ , hence:

$\Delta E=2500 J + 7655 J=10155 J$

b) In this case $Q=12.4 J$ and $W=4.2 J$ , hence:

$\Delta E=12.4 J + 4.2 J=16.6 J$

5 0

3 years ago