PLEASE HELP I HAVE LIMITED TIME!! How many particles of water (H20) are in a collection of snowflakes
with a mass of 0.005 g?

Explanation:

Si tomamos en cuenta el peso molecular del agua, que es equivalente a:

1 Átomo de H₂O

O = 16 gr/mol

H = 1 gr/mol

H₂O = 18 gr/mol

Teóricamente sabemos que en 1 mol de H2O habrá 18 gr.

Para obtener los moles presentes en 1 mg de H₂O, (como 1 gr = 1000 mg), decimos:

1 mol H2O …………………………..  18000 mg

       X          ……………………………   1 mg

X = 1 / 18000 = 5,56 X 10⁻⁵ moles de H20

Y para obtener la cantidad de moléculas presentes, de acuerdo a los moles, multiplicamos por el número de Avogadro (6,023 X 10²³ moléculas /mol)

Moléculas de H₂O = 5,56x 10⁻⁵ mol x 6,023 x 10²³

Moléculas de H₂O = 3,34488 x10¹⁹ moléculas de H₂O

En el copo de nieve habrá 3,34488 x 10¹⁹ moléculas de H₂O.

Espero que te sirva =)

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.

idk what the question is about