1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
tankabanditka [31]
2 years ago
8

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).

You might be interested in
Chemists investigated an unknown substance and found it to have the following characteristics:
bija089 [108]

The answer is option C.

That is it is a heterogeneous mixture.

Heterogeneous mixture have the following properties:

1. Different components could be observed in the substance.

2. Different samples of the substance appeared to have different proportions of the components.

3.The components could be easily separated using filters and sorting.


7 0
3 years ago
Read 2 more answers
2.0 L of oxygen gas and 8.0 L of nitrogen gas at STP are mixed together. The gaseous mixture is compressed to occupy 2.0 L at 29
otez555 [7]

Answer:

5.5 atm

Explanation:

Step 1: Calculate the moles in 2.0 L of oxygen at STP

At STP, 1 mole of an ideal gas occupies 22.4 L.

2.0 L × 1 mol/22.4 L = 0.089 mol

Step 2: Calculate the moles in 8.0 L of nitrogen at STP

At STP, 1 mole of an ideal gas occupies 22.4 L.

8.0 L × 1 mol/22.4 L = 0.36 mol

Step 3: Calculate the total number of moles of the mixture

n = 0.089 mol + 0.36 mol = 0.45 mol

Step 4: Calculate the pressure exerted by the mixture

We will use the ideal gas equation.

P × V = n × R × T

P = n × R × T / V

P = 0.45 mol × (0.0821 atm.L/mol.K) × 298 K / 2.0 L = 5.5 atm

3 0
3 years ago
Calculate the standard emf for the following reaction:
krek1111 [17]
In order to solve this, we need to know the standard cell potentials of the half reaction from the given overall reaction.
The half reactions with their standard cell potentials are:
<span>2ClO−3(aq) + 12H+(aq) + 10e- = Cl2(g) + 6H2O(l) 
</span><span>E = +1.47 
</span>
<span>Br(l) + 2e- = 2Br- 
</span><span>E = +1.065
</span>
We solve for the standard emf by subtracting the standard emf of the oxidation from the reducation, so:
1.47 - 1.065 = 0.405 V
4 0
3 years ago
The enthalpy of vaporization of Bromine is 15.4 kJ/mol. What is the energy change when 80.2 g of Br2 condenses to a liquid at 59
Aleksandr-060686 [28]

The enthalpy of vaporization of Bromine is 15.4 kJ/mol. -7.7 kJ is the energy change when 80.2 g of Br₂ condenses to a liquid at 59.5°C.

<h3>What is Enthalpy of Vaporization ?</h3>

The amount of enthalpy or energy that must be added to a liquid substance into gas substance is called Enthalpy of Vaporization. It is also known as Latent heat of vaporization.

<h3>How to find the energy change from enthalpy of vaporization ?</h3>

To calculate the energy use this expression:

Q = n \Delta H_{\text{vapo.}

where,

Q = Energy change

n = number of moles

\Delta H_{\text{Vapo.}} = Molar enthalpy of vaporization

Now find the number of moles

Number of moles (n) = \frac{\text{Given Mass}}{\text{Molar mass}}

                                   = \frac{80.2\ g }{159.8\ g/mol}

                                   = 0.5 mol

Now put the values in above formula we get

Q = - n \Delta H_{\text{vapo.}         [Negative sign is used because Br₂ condensed here]

   = - (0.5 mol × 15.4 kJ/mol)

   = - 7.7 kJ

Thus from the above conclusion we can say that The enthalpy of vaporization of Bromine is 15.4 kJ/mol. -7.7 kJ is the energy change when 80.2 g of Br₂ condenses to a liquid at 59.5°C.

Learn more about the Enthalpy of Vaporization here: brainly.com/question/13776849

#SPJ1

8 0
1 year ago
Draw the alkyne formed when 1,1-dichloro-4-methylpentane is treated with an excess of a strong base such as sodium amide. (give
alisha [4.7K]
Co2 is correct buddy
4 0
3 years ago
Other questions:
  • What is the amount of ca3(po4)2 that can be prepared from a mixture of 9g of Ca(OH) 2 and 11g of H3po4?
    9·1 answer
  • The molecule CH20 contains two single bonds and one double bond.<br> True<br> False
    7·1 answer
  • HELP PLEASE HELP ME!
    10·1 answer
  • On a balance, you have beakers of AgNO3AgNO3 solution and NaClNaCl solution. When mixed, they will form AgCl(s)AgCl(s). What wil
    12·1 answer
  • Question 1 (1 point)
    7·1 answer
  • PLEASE SOMEONE! The density of the acetic acid solution is 1.05 g/mL. Calculate the %(m/m) of the acetic acid solution (convert
    12·1 answer
  • Which statement is true concerning the Haber Process?
    9·1 answer
  • Ming has two unknown substances. One is nonpolar, and the other is polar.
    7·2 answers
  • What is it called when only the needed genes are transcribed and translated in
    6·1 answer
  • The coefficient of performance (cop) of a refrigerator is defined as the ratio of?
    12·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!