1. 4 electrons
2. Ernest Rutherford
3. Discovered the existence of a center of atom
4. 17 protons
Answer:
Advantages :they are used for seeing chemical reactions .
they are used for doing chemical experiment .
they are used for making affective medicines .
Disadvantages :they harms to our environment.
they can make side effects in our body by affective medicines made by chemicals.
while doing different unknown experiments they make explosions which can also harm to us.
I think the answer will be homogeneous mixture
First: the coefficients give the number of molecules (or atoms) involved in the reaction. In the example reaction, two molecules of hydrogen react with one molecule of oxygen and produce two molecules of water. Second: the coefficients give the number of moles of each substance involved in the reaction.
Answer:
Indeed, the two samples should contain about the same number of gas particles. However, the molar mass of 
is larger than that of 
(by a factor of about 
.) Therefore, the mass of the sample is significantly larger than that of the sample.
Explanation:
The and the sample here are under the same pressure and temperature, and have the same volume. Indeed, if both gases are ideal, then by Avogadro's Law, the two samples would contain the same number of gas particles ( and molecules, respectively.) That is:
.
Note that the mass of a gas 
is different from the number of gas particles 
in it. In particular, if all particles in this gas have a molar mass of 
, then:
.
In other words,
.
.
The ratio between the mass of the and that of the sample would be:
.
Since by Avogadro's Law:
.
Look up relative atomic mass data on a modern periodic table:
Therefore:
.
.
Verify whether 
:
- Left-hand side:
. - Right-hand side:
.
Note that the mass of the sample comes with only two significant figures. The two sides of this equations would indeed be equal if both values are rounded to two significant figures.
:
.
:
.