Answer:
Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons. Thomson's plum pudding model of the atom had negatively-charged electrons embedded within a positively-charged "soup.
Elements with three p-electrons....
That would be N, P, As, Sb, and Bi -- elements in group 15
For example, energy diagram showing "empty" orbitals up through the 3p.
.....3p __ __ __
3s __
.....2p __ __ __
2s __
1s __
Energy diagram of phosphorous showing three unpaired electrons in 3p-sublevel
.....3p ↑_ ↑_ ↑_
3s ↑↓
.....2p ↑↓ ↑↓ ↑↓
2s ↑↓
1s ↑↓
According to Hund's rule, the electrons singly occupy the p-orbitals, and all have the same spin.
Answer:
Radioactive dating
Explanation:
Radioactive dating measures the ratio of C¹²(normal) and C¹⁴ (radioactive) in fossils to determine the exact age of the specimen. C¹⁴ is unstable and has a half life of 5730 years, so as the organism ages the amount of C¹⁴ diminishes but the amount of C¹² remains constant. The ratio of C¹⁴ to C¹² is used to analyze the decay of atomic particles to determine exact age.
The simple trick which one can consider in such problem where it is asked for positron emission is :
<span>When the atomic number goes DOWN by one and mass number remains unchanged, then a positron is emitted.
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<span>a. </span>

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Here the atomic number decreases by one.
Similarly, options b and d are eliminated.
Option c is also not the answer.
For c, Count the atomic number on left side and compare it with right side. You will see it is 9 on left and 8 on right. Atomic no. did go down by 1. But the atomic mass is changed as well.
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Answer:
Boiling water is an example of a physical change and not a chemical change because the water vapor still has the same molecular structure as liquid water (H2O).
Explanation: