Answer:
1) Ca: [Ar]4s²
2) Pm: [Xe]6s²4f⁵
Explanation:
1) Ca:
Its atomic number is 20. So it has 20 protons and 20 electrons.
Since it is in the row (period) 4 the noble gas before it is Ar, and the electron configuration is that of Argon whose atomic number is 18.
So, you have two more electrons (20 - 18 = 2) to distribute.
Those two electrons go the the orbital 4s.
Finally, the electron configuration is [Ar] 4s².
2) Pm
The atomic number of Pm is 61, so it has 61 protons and 61 electrons.
Pm is in the row (period) 6. So, the noble gas before Pm is Xe.
The atomic number of Xe is 54.
Therefore, you have to distribute 61 - 54 = 7 electrons on the orbitals 6s and 4f.
The resultant distribution for Pm is: [Xe]6s² 4f⁵.
answer is A
The kinetic theory is used to explain the behaviour of gases.
One of the assumptions states that "a gas is composed of a large number of identical molecules moving at different speeds".
The sun is a star.
If you were talking about that
Answer:
It would have a charge of +2.
Explanation:
A proton has a charge of +1, an elctron has a charge of -1, and a neutron has a charge of 0. Ignore the neurons since they have a charge of 0. Since there are 20 protons and 18 electrons (20-18), the overall charge of the atom is +2.
Answer :
A car stopped at the top of a hill
Explanation :
Definition of potential energy : energy stored that depends upon the relative position of various parts of a system