<span>The smallest unit of an element that retains all the characteristics of that element is called an A. atom.
Atoms consist of protons, electrons, and neutrons, but they are particles and don't have the characteristics of the element which is why D is incorrect. B and C are not the smallest units - atoms are smaller than them.
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When air pressure is low it is Cold
Answer:
.Heat energy can be transferred from one object to another. The transfer or flow due to the difference in temperature between the two objects is called heat.
Explanation:
The transfer of thermal energy is called heat. In this process, thermal energy moves through a substance. For example, an ice cube has heat energy and so does a glass of lemonade.
Answer : The correct option is, (B) 273.15 K and 1 atm
Explanation :
STP : STP stands for standard temperature and pressure.
STP conditions :
The temperature is, 
or 
or 
The pressure is, 
or 
The volume is 22.4 L for 1 mole of a substance.
Hence, the correct option is, (B) 273.15 K and 1 atm
<u>¹⁴₇N</u><u> </u>is the more stable isotope
<h3>
Briefly explained</h3>
We have ¹⁴₇N which has a neutron to proton ratio of one, and we look at ¹⁸₇N which has a neutron to proton ratio of 1.57 Again, you look at table 24 to and you see the atomic number of seven and there is really no stable isotope. It has any more than 10 neutrons.
When we have eight, protons will go down seven protons. There's really nothing stable that has more than maybe eight neutrons. So the fact that we have 11 neutrons with ¹⁸₇N suggests that this is very unstable and
¹⁴₇N is the stable isotope of the pair.
<h3>
Stable and Unstable Nuclei</h3>
An atom is electrically neutral. It contains an equal number of positively charged protons and negatively charged electrons and their charges balance. The nucleus however contains only positively charged protons which are closely packed together in a very small volume (remember neutrons have no charge).
From the laws of physics (Coulomb’s Law) one would expect that the protons being of the same charge and so close together would exert strong repulsive forces on each other. The combined gravitational force from the protons and neutrons in a nucleus is insignificant as an attractive force because their masses are so tiny.
This implies there must be an additional attractive force similar in size to the electrostatic repulsion which holds the nucleus together.
Learn more about stable and unstable nuclei
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