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
If a muriatic acid solution has a pH of 2.50, what is the hydronium ion concentration (hydronium ion concentration is also the m
Irina18 [472]

Answer:

  • [H₃O⁺] = 0.032 M

Explanation:

The acidity of a solution is measured by its pH, which is the logarithm of the inverse of the molar concentration of hydronium (H₃O⁺) ions:

  • pH = log 1 / [H₃O⁺] = - log [H₃O⁺]

When you know the pH value you can find hydronium concentration using the antilogaritm function:

pH=-log[H_3O^{+}]\\ \\ {[H_3O^+]}=10^{-pH}\\ \\ {[H_3O^+]}=10^{-2.50}\\ \\ {[H_3O^+]}=0.0032

The unit of molar concentration is M.

To prove your answer you can take the logarithm of 0.0316:

  • log (0.0032) ≈ 2.500

5 0
3 years ago
A chemical reaction that has the general formula of nA → (A)n is best classified as a reaction.
azamat
Polymerization

For example:
nCH₂=CH₂ ---p,T,kat.----> -[-CH₂-CH₂-]- n
4 0
3 years ago
Read 2 more answers
A piece of potassium metal is added to water in a beaker. The reaction that takes place is 2K(s) 2H20(/) ..... 2KOH(aq) H2(g) Pr
kakasveta [241]

Answer:

Explanation:

The given reaction is exothermic . So ΔH is negative .

Gas is evolving so work done by gas is positive or w is positive.

Change in internal energy that is ΔU is negative.

q = u - w

u is negative , w is positive so q is negative .

4 0
3 years ago
How many gallons of 80% antifreeze solution must be mixed with 60 gallons of 20% antifreeze to get a mixture that is 70% antifre
Anarel [89]
Let A be the 80% solution and B be the 20% solution and P be the produce solution of 70%. Va and Vb and Vp are the volumes of A and B and P respectively.
Va + 60 = Vp
0.7Vp = 0.8Va + 0.2(60)
Substituting the value of Vp from the first equation:
0.7(Va + 60) = 0.8Va + 12
30 = 0.1Va
Va = 300 gallons
6 0
3 years ago
Read 2 more answers
3. Determine the pH of each of the following solutions. (Hint: See Sample Problem B.) a. 1.0 x 10-2 M HCI c. 1.0 x 10-MHI b. 1.0
densk [106]

Answer:

a. pH = 2 b. pH = 3 c. pH = 1 d. Unanswerable

Explanation:

pH = -log[H+] OR pH = -log{H3O+]

                    and inversely

pOH = -log[OH-]

1. Determine what substance you are working with, (acid/base)

2. Determine whether or not that acid or base is strong or weak.

a. 1.0 x 10^-2M HCl

HCl is a strong acid, therefore it will dissociate completely into H+ and Cl- with all ions going to the H+, therefore, the concentration of HCl and concentration of H+ are going to be equal, meaning we simply take the negative logarithm of the concentration of HCl and that would equal pH

pH = -log[H+]

pH = -log(1.0x10^-2)

pH = 2

b. 1.0 x 10^-3M HNO3

HNO3 like part a, is a strong acid, therefore it would simply require you to take the negative logarithm of the concentration of the compound itself, to find its pH.

pH = -log[H+]

pH = -log(1.0 x 10^-3)

pH = 3

c. 1.0 x 10^-1M HI

Like the previous parts, HI is a strong acid

pH = -log[H+]

pH = -log(0.10)

pH = 1

d. HB isn't an element, nor is it a compound so that would be unanswerable.

3 0
3 years ago
Other questions:
  • Suppose that Max and Maria recorded data from
    9·2 answers
  • A water molecule is composed of two hydrogen atoms and one oxygen atom arranged in a bent shape. Since oxygen is significantly m
    10·2 answers
  • What is the volume of liquid in this graduated cylinder? Be sure your answer has a reasonable number of decimal places.
    9·1 answer
  • Given the reaction 2NaOH + H2SO4 = Na2SO4 + 2H2O, what is the total number of grams of NaOH needed to react completely with 196
    13·1 answer
  • Two aqueous NaCl solutions of equal volume and concentration were kept in flasks and held at different temperatures. The two sol
    10·1 answer
  • PH of a 0.00072 M HCl solution.
    5·1 answer
  • Is the cell wall factory part or worker? And please explain what the worker or factory part does. (Don’t tell me it’s on quizlet
    9·1 answer
  • 50 + 50 - 25 x 0 + 5 + 5 =​
    8·2 answers
  • Transparency is a ____<br> of matter.<br><br> property<br> substance<br> type
    12·2 answers
  • A model for a potential chemical reaction is shown here. Evaluate the model and the reaction shown. Which statements are correct
    6·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!