Answer:
The electrons in oxygen are paired while in nitrogen, they are not.
Explanation:
To analyse this we start with writing out the ground state electronic configurations for both elements.
Oxygen: 1s²2s²2p4 meaning the p subshell has the following arrangement of electrons ↑↓ ↑ ↑
Nitrogen : 1s²2s²2p³ meaning the p subshell has the following arrangement of electrons ↑ ↑ ↑
Clearly the paired electron in oxygen will be experiencing repulsion from the electron it shares an orbital with causing it to be removed easily. The electrons in nitrogen are unpaired, each orbital is singly occupied
I think it is "A'' 'It moves along straight lines in air and changes direction when it enters water.
Answer:
a) The car was moving at a speed of 
b) The negative sign of 
denotes that the observer is coming towards the police car which is the source of the sound.
c) 
Explanation:
Given:
- original frequency of the source,
- speed of the source,
- velocity of the obstacle car be,
- speed of sound,
- observed frequency,
<u>Using the equation from the Doppler's effect:</u>
a)
The car was moving at a speed of
b)
The negative sign of denotes that the observer is coming towards the police car which is the source of the sound.
c)
Now when, 
Then, 
Using the Doppler's eq.:
