Answer:
38.7%
41.3%
20%
Explanation:
The percentage composition helps to know the what percent of the total mass of a compound is made up of each of the constituent elements or groups.
To solve this problem:
- find the formula mass by adding the atomic masses of the atoms that makes up the compound.
- place the mass contribution of the element or group to the formula mas and multiply by 100;
Compound:
Ca₃(PO₄)₂
Formula mass = 3(40) + 2[31 + 4(16)]
= 120 + 2(95)
= 120 + 190
= 310
%C = 
x 100 = 38.7%
%P = 
x 100 = 41.3%
%O = 
x 200 = 20%
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.
Answer:
wave speed slow down as it hits different material
Answer:
170 g
Explanation:
Moles of Oxygen gas :
Given, Mass of Oxygen = 80.0 g
Molar mass of Oxygen gas= 31.998 g/mol
The formula for the calculation of moles is shown below:
Thus,
The reaction between Al and O₂ is shown below as:
4Al + 3O₂ ⇒ 2Al₂O₃
From the reaction,
3 moles of O₂ on reaction forms 2 moles of Al₂O₃
1 mole of O₂ on reaction forms 2/3 moles of Al₂O₃
2.5 moles of O₂ on reaction forms (2/3)*2.5 moles of Al₂O₃
Moles of Al₂O₃ = 1.6667 moles
Molar mass of Al₂O₃ = 102 g/mol
Mass = Moles * Molar mass = 1.6667 * 102 g = 170 g
