What is the difference between the number of electrons in an atom of selenium and the number of electrons in an atom of aluminum

21 electrons

Explanation:

The number of electrons in an atom is equal to the atomic number of the element. Atomic number of aluminium is 13 and atomic number of selenium is 34. That means electrons of aluminium are 13 and electrons of selenium are 34. Thus, difference between number of electrons of these atoms is:

34 - 13 = 21 electrons

I hope it helps!

a: 45.9 meters

b: 4.29 seconds

step-by-step explanation:

a: h(t)=1/2(-9.8)(3)^2+0(3)+90

h(t)=-4.9(3)^2+90

h(t)=-44.1+90

h(t)=45.9 meters

b: 0=1/2(-9.8)(t^2)+0t+90

0=-4.9t^2+90

-90=-4.9t^2

18.37=t^2

t=4.29 seconds

in the second question, the numbers aren't exact, but they're a close approximation.

"hydrogen bonding is the attraction of h atoms in the water molecule (slight + charge) to o atoms in a neighboring water molecule (slight - charge); it is a weak interatomic force. but it is still strong enough to the water molecules "stick" together."