2. stem the mass of an atom of helium is about 4.002 atomic units.
the mass of an atom of beryllium is about 2.25 times the mass of an
atom of helium. what is the approximate mass of a beryllium atom?

The approximate mass of beryllium is 9.0045 u.

Explanation:

Given data:

mass of helium= 4.002 u

mass of beryllium which is 2.25 times of mass of helium= ?

Solution:

we will multiply the mass of helium with 2.25 times,

4.002 u × 2.25 = 9.0045 u

so the mass of beryllium atom would be 9.0045 u.

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.

explanation:

metals have excess of electrons whereas non-metals have deficiency of electrons. thus, in order to gain stability metals easily donate their electrons to the non-metals.

for example, electronic configuration of sodium is and electronic configuration of phosphorous is .

when a phosphorous atom and sodium atom combine together then sodium will donate is extra one electron to the phosphorous atom. as a result there will be formation of ionic bond between sodium and phosphorous.

the reaction will be as follows.

there, are three sodium sodium atoms and each of them will donate its one extra electron to phosphorous atom. thus, the sub-shell of phosphorous gets completely filled.  

thus, we can conclude that electrons are transferred from atoms of sodium to atoms of phosphorous. this transfer makes the sodium atoms donate one electron and the phosphorous atoms to gain one electron. as a result, the sodium and phosphorus atoms strongly attract each other.