Seeing signs of a chemical reaction does not always mean that a reaction is happening. For example, a gas (water vapor) is given off when water boils. ... You can tell that it is a physical change because water vapor can condense to form liquid water. In a chemical change, a new substance must be produced.
The answer is 3. The releasing of energy means exothermic reaction. So the ΔH should be negative. And the greatest quantity of energy released means that the greatest number. So according to the table I, the answer is 3.
Answer: The number of neutrons will increase as we move from left to right in a periodic table.
Explanation:
Atomic number is equal to the number of protons.
Mass number is the sum of number of neutrons and number of protons.
As we move from left to right, both the atomic number and mass number increases.
For example: As we move from Lithium to berrylium to boron to carbon to nitrogen to oxygen to fluorine to neon , the number of neutrons increase from 4 to 5 to 6 to 6 to 7 to 8 to 10 to 10.
Thus the number of neutrons will also increase as we move from left to right in a periodic table.
Positive ion with a radius smaller than the radius of the atom
