Which of the following represent impossible combinations of n and i? (a) 1p, (b) 4s, (c) 5f, (d) 2d 6.61

The impossible combinations of n and I are 1p and 2d.

Quantum numbers describe the position of an electron in an atom. Four sets of quantum numbers are important when discussing electrons in atoms. These quantum numbers are;

Given the conditions, combinations of n and I where n = l are not allowed. Recall that s p d f corresponds to 0 1 2 3. As such, 1p and 2d are not allowed.

Learn more: link

Explanation:

n refers to the principal quantum number, and l refers to the angular momentum or Azimuthal quantum number.

Principal quantum number (n) is used to indicate the main energy level of the electron. It may take whole numbers: 1, 2, 3, 4, 5, 6, 7, ...

Angular momentum or Azimuthal quantum number refers to the kind (shape) of the orbital. It can take numbers from 0 to n - 1.

So, if n = 1, l can only be 0; if n = 2, l can be either 0 or 1; if n = 2, l can be either 0, 1 or 2.

On the other hand, the shape of the orbitals is also representd by a letter. then there is a unique relation between the letter that represents the orbital and the angular quantum number which is:

letter       l number

s               0

p               1

d               2

f                3

The previous information is summarized in the next table:

n    possible l numbers          

1          0                                          

2         0, 1                                        

3         0, 1, 2                                    

4         0, 1, 2, 3                              

5        0, 1, 2, 3, 4

6        0, 1, 2, 3, 4, 5

7        0, 1, 2, 3, 4, 5, 6

As per the choices given in the question you have:

(a) 1 p is not possible because when n = 1 the only l number is 0 and it is an s orbital, but p ⇒ l = 1. Thus, this is a correct choice.

(b) 4s is possible since n = 4 permits l to be 0, 1, 2, and 3.

(c) 5f is possible since n = 5 permits l to be 0, 1, 2, 3, and 4.

(d) 2d is impossible since n = 2 permits l to be 0, and 1, but d ⇒ l = 2. Thus, this is other right choice.

oh it is true if thats what you are asking

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.