The nuclear symbol of an element have three parts namely:
- the symbol of an element
- mass number of the element
- atomic number of the element
The general representation is as:
where X is the chemical symbol of the element, A is mass number of the element that is total number of neutrons and protons in the nucleus of an atom, and Z is atomic number of the element that is number of protons in the atom.
Element = Gallium, 
(given)
Number of neutrons = 40 (given)
Let the nuclear symbol be 
. So, we need to determine the values of "?" in the symbol.
Atomic number of Gallium, = 31
Since, atomic number = Number of protons.
So, number of protons of Gallium, = 31
Mass number = number of protons + number of neutrons
Substituting the values:
Mass number = 
So, the nuclear symbol is 
.
This is a fill in the blanks question.
This is where the blanks are: A __________ is scientific knowledge established through direct observation and remains constant. Scientific knowledge can change when scientists _____________
The answer is followiing.
Answer: A <em>law</em> is scientific knowledge established through direct observation and remains constant. Scientific knowledge can change when scientists <em>find new evidence</em>.
Explanation:
A scientific law describes the relation (usually in mathematical terms) of natural phenomena and is supported by numerous observations and experiments. The laws are established when all the observations and result show that all the facts obey the same relation. For instance, the Universal law of gravitation: all the objects are attracted with a force that is directly proportional to the product of their masses and inversely related to the square of the distance that separates them: in lay terms, everything that goes up has to go down, and you do not expect that when a parachutist jumps out of an airplane he or she does not fall on the ground.
On the other hand, a scientific theory, although is an explanation that has been repeatedly tested and verified, is always under scientific scrtutiny and, as additional evidence is gathered it can be modified or replaced by a new theory. That is why it is said that scientific theories have to be testable and falsiable: if it is not testable and falsiable then it is not a scientific theory.
Scientific theories are aimed to describe, explain and make predictions about the objectivable world.
Answer: The rates of production of 
is 
mol/Ls and 
is 0.0195 mol/Ls.
Explanation:
Rate with respect to reactants is shown by negative sign as the reactants are decreasing with time and Rate with respect to products is shown by positive sign as the products are increasing with time.
Rate of the reaction=![-\frac{1}{4}\frac{[d[PH_3]}{dt}=\frac{[d[P_4]}{dt}=\frac{1}{6}\frac{[d[H_2]}{dt}](https://tex.z-dn.net/?f=-%5Cfrac%7B1%7D%7B4%7D%5Cfrac%7B%5Bd%5BPH_3%5D%7D%7Bdt%7D%3D%5Cfrac%7B%5Bd%5BP_4%5D%7D%7Bdt%7D%3D%5Cfrac%7B1%7D%7B6%7D%5Cfrac%7B%5Bd%5BH_2%5D%7D%7Bdt%7D)
Rate of decomposition of 
Rate of production of 
Rate of production of 
It’s B
Silicon is used for electronic devices because it is an element with very special properties. One of it's most important properties is that it is a semiconductor.
