Ok well whats the questions
2n² rule:
This rule is used to determine number of electrons in particular shell.
n=1 means K shell
n=2 means L shell
n=3 means M shell
n=4means N shell
The first K shell can hold upto 2 electrons, L shell can hold up to 8, third M shell can hold up to 18and the fourth N shell can hold upto 32 electrons. This rule of arrangement of electrons according to the shell is known 2n2 rule where n means number of shell.
For example: There is one proton in the nucleus of hydrogen atom, which moves in K shell path. It has no neutron.
The endocrine system<span> is the collection of </span>glands<span> of an organism that </span>secrete hormones<span>directly into the </span>circulatory system<span>to be carried towards distant target organs. In </span>humans<span>, the major </span>endocrine glands<span> include the </span>pineal gland<span>, </span>pituitary gland<span>, </span>pancreas<span>, </span>ovaries<span>, </span>testes<span>, </span>thyroid gland<span>, </span>parathyroid gland<span>, and </span>adrenal glands<span>. In </span>vertebrates<span>, the </span>hypothalamus<span> is the neural control center for all endocrine systems. The field of study dealing with the endocrine system and its disorders is </span>endocrinology<span>, a branch of </span>internal medicine.<span>
</span>
Aq means it's soluble in H2O by default
s means it's solid, not soluble.