Nuclei

What are the number of neutrons and the number of electrons in the neutral atom of ${}_{78}{}^{195}Pt$?

Nucleons are

Write a short note on discovery of neutron.

Write general notation of the nucleus of element X. What each term denotes?

A periodic table might list the average atomic mass of magnesium as being $24.312 \mathrm{u}$, which is the result of weighing the atomic masses of magnesium isotopes according to their natural abundances on Earth. The three isotopes and their masses are ${\mathrm{Mg}}^{24} \left(23.985 04 \mathrm{u}\right)$, ${\mathrm{Mg}}^{25} \left(24.985 84 \mathrm{u}\right)$ and ${\mathrm{Mg}}^{26} \left(25.982 59 \mathrm{u}\right)$. The natural abundance of ${\mathrm{Mg}}^{24}$ is $78.99\%$ by mass (that is $78.99\%$ of the mass of a naturally occurring sample of magnesium is due to the presence of ${\mathrm{Mg}}^{24}$). What is the abundance of (a) ${\mathrm{Mg}}^{25}$ and (b) ${\mathrm{Mg}}^{26}$?

Identify $X$ in the following nuclear reactions. 

$\left(a\right)$ ${}^{1}H+{}^{13}Al\to$$X+n$ 

$\left(b\right)$ ${ }^{29}Cu{+}^{1}H\to X$ 

$\left(c\right)$${}^{15}N{+}^{1}H{\to }^{4}He+X$.

Two stable isotopes of lithium ${}_3{}^6\mathrm{L}\mathrm{i}$ and ${}_3{}^7\mathrm{L}\mathrm{i}$ have respective abundances of $7.5\%$ and $92.5\%$. These isotopes have masses $6.01512 \mathrm{u}$ and $7.01600 \mathrm{u}$, respectively. Find the atomic mass of lithium