2. How many moles of fluorine are required to produce 12.0 grams of
KrFo? Given the equation: Kr + 3 F2 → KrF

0.0984mol of F2

Explanation:

The equation for the reaction is given below:

Kr + F2 → KrF2

Let us convert 12g of KrF2 to mole. This is illustrated below

Molar Mass of KrF2 = 84 + (2x19) = 84 + 38 = 122g/mol

Mass of KrF2 = 12g

Number of mole = Mass /Molar Mass

Number of mole of KrF2 = 12/122 = 0.0984mol

From the equation,

1mole of F2 produced 1mole of KrF2.

Therefore 0.0984mol of F2 will produce 0.0984mol of KrF2

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.