Give the number of protons, electrons, and neutrons in neutral atoms of each of the following isotopes: $$\text { (a) } \frac{10}{5} \mathrm{B}$$ $$\text { (b) } \begin{array}{l} 199 \\ 80 \end{array}$$ $$\text { (c) } \frac{63}{29} \mathrm{Cu}$$ $$\text { (e) } \begin{array}{l} 77 \text { Se } \\ 34 \end{array}$$

The atomic number, often represented by the symbol 'Z', is a fundamental property of an atom. It signifies the number of protons present in the nucleus of an atom and is unique to each chemical element. Protons carry a positive charge, and because atoms are electrically neutral overall, the atomic number also indicates the number of electrons in an uncharged atom. For example, all carbon atoms have an atomic number of 6, which means that every carbon atom has 6 protons and 6 electrons.
When identifying isotopes, the atomic number is crucial because it defines the element. An increase or decrease in the atomic number would create a different element entirely. In exercises where you're given symbols like \( \frac{63}{29} \mathrm{Cu} \), the lower number, 29, represents the atomic number of copper, assuring us that the element is indeed copper and has 29 protons and electrons.

Moving on to the mass number, which is denoted by 'A', it represents the total number of protons and neutrons in an atom's nucleus. Mass number is a whole number and determines the isotope of an element. Unlike the atomic number, the mass number is not fixed for a given element as an element can have different numbers of neutrons in its nucleus, leading to various isotopes. For example, in the isotopic notation \( \begin{array}{l} 77 \ 34 \end{array} \mathrm{Se} \), the 77 represents the mass number of Selenium, telling us that the total number of protons and neutrons adds up to 77. If you know the atomic number (34 for Selenium), you can subtract it from the mass number to find the number of neutrons: 77 (mass number) - 34 (atomic number) = 43 neutrons.
The mass number is significant when calculating the relative atomic mass of an element because isotopes with higher mass numbers will weigh more. This concept is particularly important in topics like radioactive decay and nuclear reactions, where isotopes with different mass numbers can behave quite differently.

Lastly, let's explore the subatomic particles — protons, electrons, and neutrons. These particles compose the atom, each with unique properties affecting atomic behavior. Protons, found in the nucleus, are positively charged and give the atom its identity (atomic number). Neutrons, also located in the nucleus, are neutral and add to the atom's mass without affecting its charge. Electrons orbit the nucleus and are negatively charged, balancing the positive charge of protons in a neutral atom.
Isotopes are variants of elements that have the same number of protons but different numbers of neutrons. For example, in the isotope \( \frac{10}{5} \mathrm{B} \), the mass number is 10 and the atomic number is 5; thus, it has 5 protons, 5 electrons, and 5 neutrons. Identifying the number of these subatomic particles helps in visualizing the atomic structure and is essential for understanding chemical reactions. Protons and electrons determine the chemical behavior of an atom, while the neutrons can explain the stability or radioactivity of an isotope. Understanding the balance between protons, electrons, and neutrons in an atom or isotope lays the foundation for comprehending more complex concepts in chemistry and physics.