Alkaline earth metal are the elements present in II group in the periodic table and are known as 'Metals' and have a charge of +2.
Alkaline earth metals - Be , Mg Ca, Sr , Ba, Ra
Halogens are present in VII A group in the periodic table and are 'Non-metals' and have a charge of -1.
Halogens - F, Cl, Br, I, At
When Alkaline earth metal (metals) combine with Halogens (non-metals) the compound formed will be ionic compound and the formula of the compound will be based on the charges of the element.
When we write the formula of the ionic compound the charges of the elements get criss crossed.
For example - Mg (Alkaline earth metal) have a charge of +2 and Cl (Halogen) have a charge of -1 and when they combine to form the formula their charges get criss crossed and we will get 
or 
When an alkaline earth metal, A, reacts with a halogen, X, the formula of the Ionic compound formed should be 
Answer:
mass of CO = 210.42 g
mass in three significant figures = 210. g
Explanation:
Given data:
mass of Fe2O3 = 0.400 Kg
mass of CO= ?
Solution:
chemical equation:
Fe2O3 + 3CO → 2Fe + 3CO2
Now we will calculate the molar mass of Fe2O3 and CO.
Molar mass of Fe2O3 = (55.845 × 2) + (16 × 3) = 159.69 g/mol
Molar mass of CO = 12+ 16 = 28 g/mol
now we will convert the kg of Fe2O3 in g.
mass of Fe2O3 = 0.400 kg × 1000 = 400 g
number of moles of Fe2O3 = 400 g/ 159.69 g/mol = 2.505 mol
mass of CO = moles of Fe2O3 × 3( molar mass of CO)
mass of CO = 2.505 mol × 84 g/mol
mass of CO = 210.42 g
mass in three significant figures = 210. g
Answer:
The Mitochondria
Explanation:
Mitochondria are membrane-bound cell organelles that generate most of the energy required to power the cell's organic chemistry reactions. Energy created by the mitochondria is kept in a tiny molecule known as adenosine triphosphate (ATP).
Answer :
(1) The frequency of photon is, 
(2) The energy of a single photon of this radiation is 
(3) The energy of an Avogadro's number of photons of this radiation is, 11.97 J/mol
Explanation : Given,
Wavelength of photon = 
(1 m = 100 cm)
(1) Now we have to calculate the frequency of photon.
Formula used :
where,
= frequency of photon
= wavelength of photon
c = speed of light = 
Now put all the given values in the above formula, we get:
The frequency of photon is,
(2) Now we have to calculate the energy of photon.
Formula used :
where,
= frequency of photon
h = Planck's constant = 
Now put all the given values in the above formula, we get:
The energy of a single photon of this radiation is
(3) Now we have to calculate the energy in J/mol.
The energy of an Avogadro's number of photons of this radiation is, 11.97 J/mol
