Valence electrons is an outer shell electron that is associated with an atom, and that can participate in the formation of a chemical bond if the outer shell is not closed. In a single covalent bond, both atoms in the bond contribute one valence electron in order to form a shared pair.
The presence of valence electrons can determine the elements chemical properties, such as its valence—whether it may bond with other elements and, if so, how readily and with how many. In this way, a given element's reactivity is highly dependent upon its electronic configuration. For a main group element, a valence electron can exist only in the outermost electron shell; in a transition metal, a valence electron can also be in an inner shell.
An atom with a closed shell of valence electrons (corresponding to an electron configuration s2p6 for main group elements) tends to be chemically inert. Atoms with one or two valence electrons more than a closed shell are highly reactive due to the relatively low energy to remove the extra valence electrons to form a positive ion. An atom with one or two electrons less than a closed shell is reactive due to its tendency either to gain the missing valence electrons and form a negative ion, or else to share valence electrons and form a covalent bond.
Similar to a core electron, a valence electron has the ability to absorb or release energy in the form of a photon. An energy gain can trigger the electron to move (jump) to an outer shell; this is known as atomic excitation. Or the electron can even break free from its associated atom's shell; this is ionization to form a positive ion. When an electron loses energy (thereby causing a photon to be emitted), then it can move to an inner shell which is not fully occupied.
When forming ions, elements typically gain or lose the minimum number of electrons necessary to achieve a full octet. For example, fluorine has seven valence electrons, so it is most likely to gain one electron to form an ion with a 1- charge.
The molarity of sucrose solution is 0.19 M.
The molarity of HCl is 12.8 M.
<u>Explanation:</u>
a. Molarity can be found by finding its moles and volume of water in L and then dividing both(moles divided by volume in Litres).
Mass of sucrose = 318. 6 g
Molar mass of sucrose = 342.3 g/mol
Moles = 
= 
= 0.93 moles
Mass of water = 4905 g
Density of water = 1000 g/L
Volume = 
= 
= 4.905 L
Now we can find the molarity = 
= 
= 0.19 M
So the molarity of sucrose solution is 0.19 M.
b. The molarity of HCl can be found as follows.
It is given that 39% HCl that means it contains 39 g of acid in 100 g of water.
Density of the solution is 1.20 g/mL, from this mass can be found as,
= 1200 g
Now we have to find out the amount of HCl in grams as,
= 468 g HCl
Now we have to find the number of moles,
moles = 
= 12.8 moles
Molarity of HCl = 
= 12.8 M
So the molarity of HCl is 12.8 M.
The correct answer for the question that is being presented above is this one: "A. The accepted model of the atom was changed.<span>" </span>J J Thomson discovered the electrons and performed experiment using the cathode ray tube
Here are the following choices:
<span>A. The accepted model of the atom was changed.
B. The accepted model of the atom was supported.
C. Cathode ray tubes were no longer used in experiments due to poor results.
D. Cathode ray tubes became the only instrument of use in the study of atoms</span>
Answer : Yes , H2SO4 is an arrhenius acid
<h2>Explanations : </h2>
• An ,Arrhenius acid ,is a substance that ,dissociates, in water to form ,hydrogen ions (H+).
,
• In other words, an arrhenius acid increases the H+ ion concentration in aqueous solution.
,
• This can be represented by the equation :
• Therefore, H2SO4 is a strong arrhenius acid.
You will know;
1. know what products are
2. know how they work
