There are several formulas for distance. The one you choose to use is the one that expressed distance in terms of the information that you already have.
For example, if you already know the speed and the time you've been traveling, then the formula for the distance you've covered is
D = (speed) times (time) .
Answer:
25th electron
Explanation:
the last electron is the valence electron. Assuming it has equal numbers of protons and electrons, then the 25th electron is the valence.
Explanation:
The four quantum numbers gives the position of the orbital, its spatial orientation, the shape of the orbital and the spin of the an electron in the orbital.
The principal quantum number(n) gives the main energy level in which the orbital is located; n = 1,2,3,4....
Azimuthal or secondary quantum number (l) gives the shape of the orbitals an they take values l = 0,1,2,3.... and their names are s for 0, p for 1, d for 2 and f for 3.
Magnetic quantum number gives the spatial orientation or degeneracy of the orbitals in the subshell.
Spin quantum number gives the spinning of the electrons
Electronic configuration:
Na = 1s² 2s² 2p⁶ 3s¹
The last electron enters the 3s¹
n = 3
l = 0
m = 0
spin =+ or - 
N = 1s² 2s² 2p³
last electron enters 2p³
n = 2
l = 1
m = -1, 0, 1
spin = + or - 
O = 1s² 2s² 2p²
last electron enters 2p²
n = 2
l = 1
m = -1, 0, 1
spin = + or - 
Cl =1s² 2s² 2p⁶ 3s² 3p⁵
last electron enters 3p⁵
n = 3
l = 1
m = -1, 0, 1
spin = + or - 
S = 1s² 2s² 2p⁶ 3s² 3p⁴
last electron enters 3p⁴
n = 3
l = 1
m = -1, 0, 1
spin = + or - 
learn more:
Quantum number brainly.com/question/9288609
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