atoms are made of 3 types of sub atomic particles- protons, neutrons and electrons
from these 3 particles, electrons are responsible for participating in chemical bonds. therefore chemical properties of elements are based on the number of electrons present.
valence electrons are the number of electrons in the outermost energy shell that are involved in chemical bonds.
atoms with same number of valence electrons are grouped in to columns called groups.
therefore elements of the same group have same number of valence electrons, hence similar chemical properties.
from the options given
only Be and Mg belong to the same group they both belong to group 2 with 2 valence electrons
therefore Be and Mg have similar chemical properties
answer is
1) Be and Mg
Answer : The chemical formula for the compound is, 
Explanation :
When the element 'M' react with the 
to give .
The balanced chemical reaction is,
In this reaction, 'M' is in mono-atomic form and is in diatomic form.
By the stoichiometry,
2 moles 'M' react with the 1 mole of to give 2 moles of .
Therefore, the chemical formula of the compound is,
Answer:
The radius of the centrifuge.
Explanation:
Hello,
Since the radius of the centrifuge is just a design parameter, it wouldn't be a cause of failure because it is used to know how many tubes could be fitted in into the centrifuge. On the other hand, keeping you attention away from other factors could turn into a failure as long as the sample could be poured down or just turn out inadequate for the expected results.
Best regards.
To determine the heat required in order to decompose a certain amount of a substance, we need information on the heat needed to decompose one mole of the substance. This value are readily available online and other sources. For this reaction, the heat needed is 129 kJ per 2 mol of NaHCO3. We calculate as follows:
129 KJ / 2 mol NaHCO3 (1 mol / 84.01 g ) (25.5 g NaHCO3 ) = 19.58 kJ of heat is needed.
<span>number of moles= mass / molecular mass
mass=131.50g
molecular mass of Zn(NO3)2 =189.39 g/mol
number of moles = 131.50 g/189.39 g/mol =0.69433 mol</span>
